diff --git a/src/Mod/Part/Gui/TaskAttacher.cpp b/src/Mod/Part/Gui/TaskAttacher.cpp
index 627d3cd74d..1bab787d0d 100644
--- a/src/Mod/Part/Gui/TaskAttacher.cpp
+++ b/src/Mod/Part/Gui/TaskAttacher.cpp
@@ -37,6 +37,7 @@
 #include <Base/Interpreter.h>
 #include <App/Application.h>
 #include <App/Document.h>
+#include <Gui/DocumentObserver.h>
 #include <App/Origin.h>
 #include <App/OriginFeature.h>
 #include <App/Part.h>
@@ -111,9 +112,9 @@ TaskAttacher::TaskAttacher(Gui::ViewProviderDocumentObject *ViewProvider,QWidget
       ViewProvider(ViewProvider)
 {
     //check if we are attachable
-    if(!ViewProvider->getObject()->hasExtension(Part::AttachExtension::getExtensionClassTypeId()))
-        throw Base::Exception("Object has no PArt::AttachExtension");
-    
+    if (!ViewProvider->getObject()->hasExtension(Part::AttachExtension::getExtensionClassTypeId()))
+        throw Base::RuntimeError("Object has no Part::AttachExtension");
+
     // we need a separate container widget to add all controls to
     proxy = new QWidget(this);
     ui = new Ui_TaskAttacher();
@@ -207,9 +208,11 @@ TaskAttacher::TaskAttacher(Gui::ViewProviderDocumentObject *ViewProvider,QWidget
     updatePreview();
 
     // connect object deletion with slot
-    auto bnd = boost::bind(&TaskAttacher::objectDeleted, this, _1);
+    auto bnd1 = boost::bind(&TaskAttacher::objectDeleted, this, _1);
+    auto bnd2 = boost::bind(&TaskAttacher::documentDeleted, this, _1);
     Gui::Document* document = Gui::Application::Instance->getDocument(ViewProvider->getObject()->getDocument());
-    connectDelObject = document->signalDeletedObject.connect(bnd);
+    connectDelObject = document->signalDeletedObject.connect(bnd1);
+    connectDelDocument = document->signalDeleteDocument.connect(bnd2);
 }
 
 TaskAttacher::~TaskAttacher()
@@ -221,13 +224,22 @@ TaskAttacher::~TaskAttacher()
     }
 
     connectDelObject.disconnect();
+    connectDelDocument.disconnect();
     delete ui;
 }
 
 void TaskAttacher::objectDeleted(const Gui::ViewProviderDocumentObject& view)
 {
-    if (ViewProvider == &view)
+    if (ViewProvider == &view) {
         ViewProvider = nullptr;
+        this->setDisabled(true);
+    }
+}
+
+void TaskAttacher::documentDeleted(const Gui::Document&)
+{
+    ViewProvider = nullptr;
+    this->setDisabled(true);
 }
 
 const QString makeHintText(std::set<eRefType> hint)
@@ -244,6 +256,8 @@ const QString makeHintText(std::set<eRefType> hint)
 
 void TaskAttacher::updateReferencesUI()
 {
+    if (!ViewProvider)
+        return;
 
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
 
@@ -274,6 +288,9 @@ void TaskAttacher::updateReferencesUI()
 
 bool TaskAttacher::updatePreview()
 {
+    if (!ViewProvider)
+        return false;
+
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
     QString errMessage;
     bool attached = false;
@@ -319,6 +336,9 @@ QLineEdit* TaskAttacher::getLine(unsigned idx)
 
 void TaskAttacher::onSelectionChanged(const Gui::SelectionChanges& msg)
 {
+    if (!ViewProvider)
+        return;
+
     if (msg.Type == Gui::SelectionChanges::AddSelection) {
         if (iActiveRef < 0)
             return;
@@ -405,6 +425,9 @@ void TaskAttacher::onSelectionChanged(const Gui::SelectionChanges& msg)
 
 void TaskAttacher::onAttachmentOffsetChanged(double /*val*/, int idx)
 {
+    if (!ViewProvider)
+        return;
+
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
     Base::Placement pl = pcAttach->AttachmentOffset.getValue();
 
@@ -447,22 +470,27 @@ void TaskAttacher::onAttachmentOffsetXChanged(double val)
 {
     onAttachmentOffsetChanged(val, 0);
 }
+
 void TaskAttacher::onAttachmentOffsetYChanged(double val)
 {
     onAttachmentOffsetChanged(val, 1);
 }
+
 void TaskAttacher::onAttachmentOffsetZChanged(double val)
 {
     onAttachmentOffsetChanged(val, 2);
 }
+
 void TaskAttacher::onAttachmentOffsetYawChanged(double val)
 {
     onAttachmentOffsetChanged(val, 3);
 }
+
 void TaskAttacher::onAttachmentOffsetPitchChanged(double val)
 {
     onAttachmentOffsetChanged(val, 4);
 }
+
 void TaskAttacher::onAttachmentOffsetRollChanged(double val)
 {
     onAttachmentOffsetChanged(val, 5);
@@ -470,6 +498,9 @@ void TaskAttacher::onAttachmentOffsetRollChanged(double val)
 
 void TaskAttacher::onCheckFlip(bool on)
 {
+    if (!ViewProvider)
+        return;
+
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
     pcAttach->MapReversed.setValue(on);
     ViewProvider->getObject()->getDocument()->recomputeFeature(ViewProvider->getObject());
@@ -493,18 +524,24 @@ void TaskAttacher::onButtonRef(const bool checked, unsigned idx)
 void TaskAttacher::onButtonRef1(const bool checked) {
     onButtonRef(checked, 0);
 }
+
 void TaskAttacher::onButtonRef2(const bool checked) {
     onButtonRef(checked, 1);
 }
+
 void TaskAttacher::onButtonRef3(const bool checked) {
     onButtonRef(checked, 2);
 }
+
 void TaskAttacher::onButtonRef4(const bool checked) {
     onButtonRef(checked, 3);
 }
 
 void TaskAttacher::onModeSelect()
 {
+    if (!ViewProvider)
+        return;
+
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
     pcAttach->MapMode.setValue(getActiveMapMode());
     updatePreview();
@@ -512,6 +549,9 @@ void TaskAttacher::onModeSelect()
 
 void TaskAttacher::onRefName(const QString& text, unsigned idx)
 {
+    if (!ViewProvider)
+        return;
+
     QLineEdit* line = getLine(idx);
     if (line == NULL) return;
 
@@ -621,13 +661,16 @@ void TaskAttacher::onRefName(const QString& text, unsigned idx)
 
 void TaskAttacher::updateRefButton(int idx)
 {
+    if (!ViewProvider)
+        return;
+
     QAbstractButton* b;
     switch(idx){
         case 0: b = ui->buttonRef1; break;
         case 1: b = ui->buttonRef2; break;
         case 2: b = ui->buttonRef3; break;
         case 3: b = ui->buttonRef4; break;
-        default: throw Base::Exception("button index out of range");
+        default: throw Base::IndexError("button index out of range");
     }
 
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
@@ -654,6 +697,9 @@ void TaskAttacher::updateRefButton(int idx)
 
 void TaskAttacher::updateAttachmentOffsetUI()
 {
+    if (!ViewProvider)
+        return;
+
     Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
     Base::Placement pl = pcAttach->AttachmentOffset.getValue();
     Base::Vector3d pos = pl.getPosition();
@@ -707,6 +753,9 @@ void TaskAttacher::updateAttachmentOffsetUI()
 
 void TaskAttacher::updateListOfModes()
 {
+    if (!ViewProvider)
+        return;
+
     //first up, remember currently selected mode.
     eMapMode curMode = mmDeactivated;
     auto sel = ui->listOfModes->selectedItems();
@@ -823,20 +872,22 @@ void TaskAttacher::onRefName1(const QString& text)
 {
     onRefName(text, 0);
 }
+
 void TaskAttacher::onRefName2(const QString& text)
 {
     onRefName(text, 1);
 }
+
 void TaskAttacher::onRefName3(const QString& text)
 {
     onRefName(text, 2);
 }
+
 void TaskAttacher::onRefName4(const QString &text)
 {
     onRefName(text, 3);
 }
 
-
 bool TaskAttacher::getFlip() const
 {
     return ui->checkBoxFlip->isChecked();
@@ -880,8 +931,8 @@ void TaskAttacher::changeEvent(QEvent *e)
 
 void TaskAttacher::visibilityAutomation(bool opening_not_closing)
 {
-    if (opening_not_closing){
-                //crash guards
+    if (opening_not_closing) {
+        //crash guards
         if (!ViewProvider)
             return;
         if (!ViewProvider->getObject())
@@ -935,7 +986,8 @@ TaskDlgAttacher::TaskDlgAttacher(Gui::ViewProviderDocumentObject *ViewProvider,
     : TaskDialog(),ViewProvider(ViewProvider), parameter(nullptr)
 {
     assert(ViewProvider);
-    
+    setDocumentName(ViewProvider->getDocument()->getDocument()->getName());
+
     if(createBox) {
         parameter  = new TaskAttacher(ViewProvider);
         Content.push_back(parameter);
@@ -952,43 +1004,57 @@ TaskDlgAttacher::~TaskDlgAttacher()
 
 void TaskDlgAttacher::open()
 {
-    
+
 }
 
 void TaskDlgAttacher::clicked(int)
 {
-    
+
 }
 
 bool TaskDlgAttacher::accept()
 {
-
     try {
+        Gui::DocumentT doc(getDocumentName());
+        Gui::Document* document = doc.getDocument();
+        if (!document || !ViewProvider)
+            return true;
+
         Part::AttachExtension* pcAttach = ViewProvider->getObject()->getExtensionByType<Part::AttachExtension>();
         std::string name = ViewProvider->getObject()->getNameInDocument();
+        std::string appDocument = doc.getAppDocumentPython();
+        std::string guiDocument = doc.getGuiDocumentPython();
 
         //DeepSOIC: changed this to heavily rely on dialog constantly updating feature properties
         if (pcAttach->AttachmentOffset.isTouched()){
             Base::Placement plm = pcAttach->AttachmentOffset.getValue();
             double yaw, pitch, roll;
             plm.getRotation().getYawPitchRoll(yaw,pitch,roll);
-            Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.%s.AttachmentOffset = App.Placement(App.Vector(%.10f, %.10f, %.10f),  App.Rotation(%.10f, %.10f, %.10f))",
-                                    name.c_str(),
+            Gui::Command::doCommand(Gui::Command::Doc,"%s.%s.AttachmentOffset = App.Placement(App.Vector(%.10f, %.10f, %.10f),  App.Rotation(%.10f, %.10f, %.10f))",
+                                    appDocument.c_str(), name.c_str(),
                                     plm.getPosition().x, plm.getPosition().y, plm.getPosition().z,
                                     yaw, pitch, roll);
         }
 
-        Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.%s.MapReversed = %s", name.c_str(), pcAttach->MapReversed.getValue() ? "True" : "False");
+        Gui::Command::doCommand(Gui::Command::Doc,"%s.%s.MapReversed = %s",
+                                appDocument.c_str(), name.c_str(),
+                                pcAttach->MapReversed.getValue() ? "True" : "False");
 
-        Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.%s.Support = %s", name.c_str(), pcAttach->Support.getPyReprString().c_str());
+        Gui::Command::doCommand(Gui::Command::Doc,"%s.%s.Support = %s",
+                                appDocument.c_str(), name.c_str(),
+                                pcAttach->Support.getPyReprString().c_str());
 
-        Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.%s.MapMode = '%s'", name.c_str(), AttachEngine::getModeName(eMapMode(pcAttach->MapMode.getValue())).c_str());
+        Gui::Command::doCommand(Gui::Command::Doc,"%s.%s.MapMode = '%s'",
+                                appDocument.c_str(), name.c_str(),
+                                AttachEngine::getModeName(eMapMode(pcAttach->MapMode.getValue())).c_str());
+
+        Gui::Command::doCommand(Gui::Command::Doc,"%s.recompute()", appDocument.c_str());
 
-        Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.recompute()");
         if (!ViewProvider->getObject()->isValid())
-            throw Base::Exception(ViewProvider->getObject()->getStatusString());
-        Gui::Command::doCommand(Gui::Command::Gui, "Gui.activeDocument().resetEdit()");
-        Gui::Command::commitCommand();
+            throw Base::RuntimeError(ViewProvider->getObject()->getStatusString());
+
+        Gui::Command::doCommand(Gui::Command::Gui, "%s.resetEdit()", guiDocument.c_str());
+        document->commitCommand();
     }
     catch (const Base::Exception& e) {
         QMessageBox::warning(parameter, tr("Datum dialog: Input error"), QString::fromLatin1(e.what()));
@@ -1000,13 +1066,16 @@ bool TaskDlgAttacher::accept()
 
 bool TaskDlgAttacher::reject()
 {
-    // roll back the done things
-    Gui::Command::abortCommand();
-    Gui::Command::doCommand(Gui::Command::Gui,"Gui.activeDocument().resetEdit()");
-    Gui::Command::doCommand(Gui::Command::Doc,"App.ActiveDocument.recompute()");
+    Gui::DocumentT doc(getDocumentName());
+    Gui::Document* document = doc.getDocument();
+    if (document) {
+        // roll back the done things
+        document->abortCommand();
+        Gui::Command::doCommand(Gui::Command::Gui,"%s.resetEdit()", doc.getGuiDocumentPython().c_str());
+        Gui::Command::doCommand(Gui::Command::Doc,"%s.recompute()", doc.getAppDocumentPython().c_str());
+    }
+
     return true;
 }
 
-
-
 #include "moc_TaskAttacher.cpp"
diff --git a/src/Mod/Part/Gui/TaskAttacher.h b/src/Mod/Part/Gui/TaskAttacher.h
index 703eb1a45d..b7f7b2d2f1 100644
--- a/src/Mod/Part/Gui/TaskAttacher.h
+++ b/src/Mod/Part/Gui/TaskAttacher.h
@@ -24,12 +24,12 @@
 #ifndef GUI_TASKVIEW_TaskAttacher_H
 #define GUI_TASKVIEW_TaskAttacher_H
 
-#include <Gui/TaskView/TaskView.h>
 #include <Gui/Selection.h>
+#include <Gui/ViewProviderDocumentObject.h>
+#include <Gui/TaskView/TaskView.h>
 #include <Gui/TaskView/TaskDialog.h>
 #include <Mod/Part/App/Attacher.h>
 
-#include "Gui/ViewProviderDocumentObject.h"
 
 class Ui_TaskAttacher;
 class QLineEdit;
@@ -90,6 +90,7 @@ protected:
     void changeEvent(QEvent *e) override;
 private:
     void objectDeleted(const Gui::ViewProviderDocumentObject&);
+    void documentDeleted(const Gui::Document&);
     void onSelectionChanged(const Gui::SelectionChanges& msg) override;
     void updateReferencesUI();
 
@@ -133,6 +134,7 @@ private:
 
     typedef boost::signals2::connection Connection;
     Connection connectDelObject;
+    Connection connectDelDocument;
 };
 
 /// simulation dialog for the TaskView