diff --git a/src/App/Metadata.cpp b/src/App/Metadata.cpp
index 692e9b6c0e..df89913f08 100644
--- a/src/App/Metadata.cpp
+++ b/src/App/Metadata.cpp
@@ -315,7 +315,7 @@ void App::Metadata::addGenericMetadata(const std::string& tag, const Meta::Gener
 void App::Metadata::removeContentItem(const std::string& tag, const std::string& itemName)
 {
     auto tagRange = _content.equal_range(tag);
-    auto foundItem = std::find_if(tagRange.first, tagRange.second, [itemName](auto check) -> bool { return itemName == check.second.name(); });
+    auto foundItem = std::find_if(tagRange.first, tagRange.second, [&itemName](auto check) -> bool { return itemName == check.second.name(); });
     if (foundItem != tagRange.second)
         _content.erase(foundItem);
 }
@@ -686,6 +686,8 @@ Meta::Url::Url(const XERCES_CPP_NAMESPACE::DOMElement* e)
         type = UrlType::readme;
     else if (typeAttribute == "documentation")
         type = UrlType::documentation;
+    else
+        type = UrlType::website;
 
     if (type == UrlType::repository) 
         branch = StrXUTF8(e->getAttribute(XUTF8Str("branch").unicodeForm())).str;
diff --git a/src/App/PropertyExpressionEngine.h b/src/App/PropertyExpressionEngine.h
index ab450e6956..c48549d7df 100644
--- a/src/App/PropertyExpressionEngine.h
+++ b/src/App/PropertyExpressionEngine.h
@@ -80,7 +80,7 @@ public:
     typedef boost::function<std::string (const App::ObjectIdentifier & path, std::shared_ptr<const App::Expression> expr)> ValidatorFunc;
 
     /**
-     * @brief The ExpressionInfo struct encapsulates an expression and a comment.
+     * @brief The ExpressionInfo struct encapsulates an expression.
      */
 
     struct ExpressionInfo {
@@ -94,10 +94,12 @@ public:
 
         ExpressionInfo(const ExpressionInfo & other) {
             expression = other.expression;
+            busy = other.busy;
         }
 
         ExpressionInfo & operator=(const ExpressionInfo & other) {
             expression = other.expression;
+            busy = other.busy;
             return *this;
         }
     };
diff --git a/src/Base/PyObjectBase.cpp b/src/Base/PyObjectBase.cpp
index ad28902bbb..7336963e7b 100644
--- a/src/Base/PyObjectBase.cpp
+++ b/src/Base/PyObjectBase.cpp
@@ -235,7 +235,8 @@ PyObject* createWeakRef(PyObjectBase* ptr)
     static bool init = false;
     if (!init) {
        init = true;
-       PyType_Ready(&PyBaseProxyType);
+       if (PyType_Ready(&PyBaseProxyType) < 0)
+           return nullptr;
     }
 
     PyObject* proxy = ptr->baseProxy;
diff --git a/src/Gui/DlgGeneralImp.cpp b/src/Gui/DlgGeneralImp.cpp
index 88a3c9f024..09fee84c9d 100644
--- a/src/Gui/DlgGeneralImp.cpp
+++ b/src/Gui/DlgGeneralImp.cpp
@@ -353,7 +353,7 @@ void DlgGeneralImp::recreatePreferencePackMenu()
         ui->PreferencePacks->setItem(row, 1, kind);
         auto button = new QPushButton(icon, tr("Apply"));
         button->setToolTip(tr("Apply the %1 preference pack").arg(QString::fromStdString(pack.first)));
-        connect(button, &QPushButton::clicked, this, [this, pack]() { onLoadPreferencePackClicked(pack.first); });
+        connect(button, &QPushButton::clicked, this, [this, &pack]() { onLoadPreferencePackClicked(pack.first); });
         ui->PreferencePacks->setCellWidget(row, 2, button);
         ++row;
     }
diff --git a/src/Gui/DlgPropertyLink.cpp b/src/Gui/DlgPropertyLink.cpp
index 511aba9878..df97c57c23 100644
--- a/src/Gui/DlgPropertyLink.cpp
+++ b/src/Gui/DlgPropertyLink.cpp
@@ -473,7 +473,12 @@ void DlgPropertyLink::detachObserver() {
 
     auto view = qobject_cast<Gui::PropertyView*>(parentView.data());
     if(view && savedSelections.size()) {
-        Gui::Selection().clearSelection();
+        try {
+            Gui::Selection().clearSelection();
+        }
+        catch (Py::Exception& e) {
+            e.clear();
+        }
         for(auto &sel : savedSelections) {
             if(sel.getSubObject())
                 Gui::Selection().addSelection(sel.getDocumentName().c_str(),
diff --git a/src/Gui/GestureNavigationStyle.cpp b/src/Gui/GestureNavigationStyle.cpp
index 8bebd5d27a..39295d9da0 100644
--- a/src/Gui/GestureNavigationStyle.cpp
+++ b/src/Gui/GestureNavigationStyle.cpp
@@ -93,7 +93,7 @@ namespace Gui {
 class NS::Event : public sc::event<NS::Event>
 {
 public:
-    Event():inventor_event(nullptr), flags(new Flags){}
+    Event():inventor_event(nullptr), modifiers{}, flags(new Flags){}
     virtual ~Event(){}
 
     void log() const {
diff --git a/src/Gui/Quarter/EventFilter.cpp b/src/Gui/Quarter/EventFilter.cpp
index 0787738b02..789c4d2f09 100644
--- a/src/Gui/Quarter/EventFilter.cpp
+++ b/src/Gui/Quarter/EventFilter.cpp
@@ -147,10 +147,10 @@ EventFilter::eventFilter(QObject * obj, QEvent * qevent)
   case QEvent::MouseButtonPress:
   case QEvent::MouseButtonRelease:
   case QEvent::MouseButtonDblClick:
-    PRIVATE(this)->trackPointerPosition(dynamic_cast<QMouseEvent *>(qevent));
+    PRIVATE(this)->trackPointerPosition(static_cast<QMouseEvent *>(qevent));
     break;
   case QEvent::Resize:
-    PRIVATE(this)->trackWindowSize(dynamic_cast<QResizeEvent *>(qevent));
+    PRIVATE(this)->trackWindowSize(static_cast<QResizeEvent *>(qevent));
     break;
   default:
     break;
diff --git a/src/Gui/Quarter/QuarterWidgetP.cpp b/src/Gui/Quarter/QuarterWidgetP.cpp
index 37547504c4..ad46e9449f 100644
--- a/src/Gui/Quarter/QuarterWidgetP.cpp
+++ b/src/Gui/Quarter/QuarterWidgetP.cpp
@@ -83,7 +83,12 @@ QuarterWidgetP::QuarterWidgetP(QuarterWidget * masterptr, const QtGLWidget * sha
   clearzbuffer(true),
   clearwindow(true),
   addactions(true),
+  processdelayqueue(true),
+  currentStateMachine(nullptr),
   device_pixel_ratio(1.0),
+  transparencytypegroup(nullptr),
+  stereomodegroup(nullptr),
+  rendermodegroup(nullptr),
   contextmenu(nullptr)
 {
   this->cachecontext = findCacheContext(masterptr, sharewidget);
diff --git a/src/Gui/SoFCSelection.cpp b/src/Gui/SoFCSelection.cpp
index 578c646178..47247c93da 100644
--- a/src/Gui/SoFCSelection.cpp
+++ b/src/Gui/SoFCSelection.cpp
@@ -160,35 +160,42 @@ void SoFCSelection::doAction(SoAction *action)
     if(useNewSelection.getValue() && action->getCurPathCode()!=SoAction::OFF_PATH) {
         if (action->getTypeId() == Gui::SoHighlightElementAction::getClassTypeId()) {
             Gui::SoHighlightElementAction* hlaction = static_cast<Gui::SoHighlightElementAction*>(action);
-            if(!hlaction->isHighlighted()) {
+            if (!hlaction->isHighlighted()) {
                 auto ctx = Gui::SoFCSelectionRoot::getActionContext(action,this,selContext,false);
-                if(ctx->isHighlighted()) {
+                if (ctx && ctx->isHighlighted()) {
                     ctx->highlightIndex = -1;
                     touch();
                 }
-            }else{
+            }
+            else {
                 auto ctx = Gui::SoFCSelectionRoot::getActionContext(action,this,selContext);
-                ctx->highlightColor = hlaction->getColor();
-                if(!ctx->isHighlighted()) {
-                    ctx->highlightIndex = 0;
-                    touch();
+                if (ctx) {
+                    ctx->highlightColor = hlaction->getColor();
+                    if (!ctx->isHighlighted()) {
+                        ctx->highlightIndex = 0;
+                        touch();
+                    }
                 }
             }
             return;
-        } else if (action->getTypeId() == Gui::SoSelectionElementAction::getClassTypeId()) {
+        }
+        else if (action->getTypeId() == Gui::SoSelectionElementAction::getClassTypeId()) {
             Gui::SoSelectionElementAction* selaction = static_cast<Gui::SoSelectionElementAction*>(action);
             if (selaction->getType() == Gui::SoSelectionElementAction::All ||
                 selaction->getType() == Gui::SoSelectionElementAction::Append) {
                 SelContextPtr ctx = Gui::SoFCSelectionRoot::getActionContext(action,this,selContext);
-                ctx->selectionColor = selaction->getColor();
-                if(!ctx->isSelectAll()) {
-                    ctx->selectAll();
-                    this->touch();
+                if (ctx) {
+                    ctx->selectionColor = selaction->getColor();
+                    if(!ctx->isSelectAll()) {
+                        ctx->selectAll();
+                        this->touch();
+                    }
                 }
-            } else if (selaction->getType() == Gui::SoSelectionElementAction::None ||
-                       selaction->getType() == Gui::SoSelectionElementAction::Remove) {
+            }
+            else if (selaction->getType() == Gui::SoSelectionElementAction::None ||
+                     selaction->getType() == Gui::SoSelectionElementAction::Remove) {
                 SelContextPtr ctx = Gui::SoFCSelectionRoot::getActionContext(action,this,selContext,false);
-                if(ctx && ctx->isSelected()) {
+                if (ctx && ctx->isSelected()) {
                     ctx->selectionIndex.clear();
                     this->touch();
                 }
@@ -965,9 +972,11 @@ SoFCSelection::setOverride(SoGLRenderAction * action, SelContextPtr ctx)
 
     Styles mystyle = (Styles) this->style.getValue();
 
-    if(mystyle == SoFCSelection::BOX) {
-        SoFCSelectionRoot::renderBBox(
-                action,this,preselected?ctx->highlightColor:ctx->selectionColor);
+    if (mystyle == SoFCSelection::BOX) {
+        if (ctx) {
+            SoFCSelectionRoot::renderBBox(
+                    action, this, preselected ? ctx->highlightColor : ctx->selectionColor);
+        }
         this->uniqueId = oldId;
         return false;
     }
@@ -979,19 +988,19 @@ SoFCSelection::setOverride(SoGLRenderAction * action, SelContextPtr ctx)
     SoMaterialBindingElement::set(state,SoMaterialBindingElement::OVERALL);
     SoOverrideElement::setMaterialBindingOverride(state,this,true);
 
-    if(!preselected)
+    if (!preselected && ctx)
         SoLazyElement::setEmissive(state, &ctx->selectionColor);
-    else
+    else if (ctx)
         SoLazyElement::setEmissive(state, &ctx->highlightColor);
     SoOverrideElement::setEmissiveColorOverride(state, this, true);
 
     if(SoLazyElement::getLightModel(state)==SoLazyElement::BASE_COLOR
             || mystyle == SoFCSelection::EMISSIVE_DIFFUSE)
     {
-        if(!preselected)
-            SoLazyElement::setDiffuse(state, this,1, &ctx->selectionColor,&colorpacker);
-        else
-            SoLazyElement::setDiffuse(state, this,1, &ctx->highlightColor,&colorpacker);
+        if (!preselected && ctx)
+            SoLazyElement::setDiffuse(state, this, 1, &ctx->selectionColor,&colorpacker);
+        else if (ctx)
+            SoLazyElement::setDiffuse(state, this, 1, &ctx->highlightColor,&colorpacker);
         SoOverrideElement::setDiffuseColorOverride(state, this, true);
     }
 
diff --git a/src/Gui/TaskView/TaskDialogPython.cpp b/src/Gui/TaskView/TaskDialogPython.cpp
index 16f6be9a25..bf828b2bd9 100644
--- a/src/Gui/TaskView/TaskDialogPython.cpp
+++ b/src/Gui/TaskView/TaskDialogPython.cpp
@@ -367,14 +367,7 @@ TaskDialogPython::~TaskDialogPython()
     Content.clear();
 
     Base::PyGILStateLocker lock;
-
-    // The widgets stored in the 'form' attribute will be deleted.
-    // Thus, set this attribute to None to make sure that when using
-    // the same dialog instance for a task panel won't segfault.
-    if (this->dlg.hasAttr(std::string("form"))) {
-        this->dlg.setAttr(std::string("form"), Py::None());
-    }
-    this->dlg = Py::None();
+    clearForm();
 
     // Assigning None to 'dlg' may destroy some of the stored widgets.
     // By guarding them with QPointer their pointers will be set to null
@@ -382,6 +375,22 @@ TaskDialogPython::~TaskDialogPython()
     Content.insert(Content.begin(), guarded.begin(), guarded.end());
 }
 
+void TaskDialogPython::clearForm()
+{
+    try {
+        // The widgets stored in the 'form' attribute will be deleted.
+        // Thus, set this attribute to None to make sure that when using
+        // the same dialog instance for a task panel won't segfault.
+        if (this->dlg.hasAttr(std::string("form"))) {
+            this->dlg.setAttr(std::string("form"), Py::None());
+        }
+        this->dlg = Py::None();
+    }
+    catch (Py::AttributeError& e) {
+        e.clear();
+    }
+}
+
 void TaskDialogPython::open()
 {
     Base::PyGILStateLocker lock;
diff --git a/src/Gui/TaskView/TaskDialogPython.h b/src/Gui/TaskView/TaskDialogPython.h
index 4d1861d521..178f562c7e 100644
--- a/src/Gui/TaskView/TaskDialogPython.h
+++ b/src/Gui/TaskView/TaskDialogPython.h
@@ -104,7 +104,10 @@ public:
     virtual bool reject();
     /// is called by the framework if the user press the help button 
     virtual void helpRequested();
-    
+
+private:
+    void clearForm();
+
 private:
     Py::Object dlg;
 };
diff --git a/src/Gui/ViewProviderLink.cpp b/src/Gui/ViewProviderLink.cpp
index 91214601c1..6d206a46f6 100644
--- a/src/Gui/ViewProviderLink.cpp
+++ b/src/Gui/ViewProviderLink.cpp
@@ -2744,6 +2744,9 @@ void ViewProviderLink::updateLinks(ViewProvider *vp) {
     catch (const Base::TypeError &e) {
         e.ReportException();
     }
+    catch (const Base::ValueError &e) {
+        e.ReportException();
+    }
 }
 
 PyObject *ViewProviderLink::getPyObject() {
diff --git a/src/Gui/ViewProviderPythonFeature.cpp b/src/Gui/ViewProviderPythonFeature.cpp
index c5e5a83db1..cf77dbf72c 100644
--- a/src/Gui/ViewProviderPythonFeature.cpp
+++ b/src/Gui/ViewProviderPythonFeature.cpp
@@ -283,7 +283,12 @@ ViewProviderPythonFeatureImp::~ViewProviderPythonFeatureImp()
 #undef FC_PY_ELEMENT
 #define FC_PY_ELEMENT(_name) py_##_name = Py::None();
 
-    FC_PY_VIEW_OBJECT
+    try {
+        FC_PY_VIEW_OBJECT
+    }
+    catch (Py::Exception& e) {
+        e.clear();
+    }
 }
 
 void ViewProviderPythonFeatureImp::init(PyObject *pyobj) {
diff --git a/src/Gui/propertyeditor/PropertyItem.cpp b/src/Gui/propertyeditor/PropertyItem.cpp
index 66deba4078..f3efc542a1 100644
--- a/src/Gui/propertyeditor/PropertyItem.cpp
+++ b/src/Gui/propertyeditor/PropertyItem.cpp
@@ -4028,13 +4028,15 @@ QWidget* PropertyFileItem::createEditor(QWidget* parent, const QObject* receiver
 void PropertyFileItem::setEditorData(QWidget *editor, const QVariant& data) const
 {
     const App::Property* prop = getFirstProperty();
-    const App::PropertyFile* propFile = static_cast<const App::PropertyFile*>(prop);
-    std::string filter = propFile->getFilter();
-    Gui::FileChooser *fc = qobject_cast<Gui::FileChooser*>(editor);
-    if (!filter.empty()) {
-        fc->setFilter(Base::Tools::fromStdString(filter));
+    if (prop) {
+        const App::PropertyFile* propFile = static_cast<const App::PropertyFile*>(prop);
+        std::string filter = propFile->getFilter();
+        Gui::FileChooser *fc = qobject_cast<Gui::FileChooser*>(editor);
+        if (!filter.empty()) {
+            fc->setFilter(Base::Tools::fromStdString(filter));
+        }
+        fc->setFileName(data.toString());
     }
-    fc->setFileName(data.toString());
 }
 
 QVariant PropertyFileItem::editorData(QWidget *editor) const