Assembly: Backport 27567 (#27628)

src/Mod/Assembly/Gui/ViewProviderAssembly.cpp

@@ -1205,6 +1205,14 @@ void ViewProviderAssembly::draggerMotionCallback(void* data, SoDragger* d)
 
 void ViewProviderAssembly::onSelectionChanged(const Gui::SelectionChanges& msg)
 {
+    // onSelectionChanged is called from both Selection.cpp and SelectionObserver.
+    // In the case where you have nested assemblies, that would cause issues. See #27532
+    bool singleAssembly
+        = getDocument()->getDocument()->getObjectsOfType<Assembly::AssemblyObject>().size() == 1;
+    if (!isInEditMode() && !singleAssembly) {
+        return;
+    }
+
     // Joint components isolation
     if (msg.Type == Gui::SelectionChanges::AddSelection) {
         auto selection = Gui::Selection().getSelection();
@@ -1498,6 +1506,8 @@ void ViewProviderAssembly::isolateJointReferences(App::DocumentObject* joint, Is
         return;
     }
 
+    clearIsolate();
+
     App::DocumentObject* part1 = getMovingPartFromRef(joint, "Reference1");
     App::DocumentObject* part2 = getMovingPartFromRef(joint, "Reference2");
     if (!part1 || !part2) {