See #4239. Ensure that all copy pasted objects are unlinked. Use duplicate if you want to copy.

src/blenderbim/blenderbim/bim/module/geometry/operator.py

@@ -1272,7 +1272,12 @@ class OverridePasteBuffer(bpy.types.Operator):
         bpy.ops.view3d.pastebuffer()
         if IfcStore.get_file():
             for obj in context.selected_objects:
-                blenderbim.core.root.copy_class(tool.Ifc, tool.Collector, tool.Geometry, tool.Root, obj=obj)
+                # Pasted objects may come from another Blender session, or even
+                # from the same session where the original object has since
+                # been deleted. As the source element may not exist, paste will
+                # always unlink the element. If you want to duplicate an
+                # element, use the duplicate commands.
+                tool.Root.unlink_object(obj)
         return {"FINISHED"}
 
 

src/blenderbim/blenderbim/tool/root.py

@@ -293,3 +293,15 @@ class Root(blenderbim.core.tool.Root):
         name = getattr(element, "Name", getattr(element, "AxisTag", None))
         obj.name = "{}/{}".format(element.is_a(), name or "Unnamed")
         obj.BIMObjectProperties.is_renaming = False
+
+    @classmethod
+    def unlink_object(cls, obj):
+        tool.Ifc.unlink(obj=obj)
+        if hasattr(obj.data, "BIMMeshProperties"):
+            obj.data.BIMMeshProperties.ifc_definition_id = 0
+        for material_slot in obj.material_slots:
+            if material_slot.material:
+                blenderbim.core.style.unlink_style(tool.Ifc, tool.Style, obj=material_slot.material)
+                blenderbim.core.material.unlink_material(tool.Ifc, obj=material_slot.material)
+        if "Ifc" in obj.name and "/" in obj.name:
+            obj.name = obj.name.split("/", 1)[1]