diff --git a/cura/CuraApplication.py b/cura/CuraApplication.py
index 342f6cb91d..7b6e970a68 100755
--- a/cura/CuraApplication.py
+++ b/cura/CuraApplication.py
@@ -1040,8 +1040,9 @@ class CuraApplication(QtApplication):
             Selection.add(node)
 
     ##  Delete all nodes containing mesh data in the scene.
+    #   \param only_selectable. Set this to False to delete objects from all build plates
     @pyqtSlot()
-    def deleteAll(self):
+    def deleteAll(self, only_selectable = True):
         Logger.log("i", "Clearing scene")
         if not self.getController().getToolsEnabled():
             return
@@ -1052,7 +1053,9 @@ class CuraApplication(QtApplication):
                 continue
             if (not node.getMeshData() and not node.callDecoration("getLayerData")) and not node.callDecoration("isGroup"):
                 continue  # Node that doesnt have a mesh and is not a group.
-            if not node.isSelectable():
+            if only_selectable and not node.isSelectable():
+                continue
+            if not node.callDecoration("isSliceable"):
                 continue  # Only remove nodes that are selectable.
             if node.getParent() and node.getParent().callDecoration("isGroup"):
                 continue  # Grouped nodes don't need resetting as their parent (the group) is resetted)
@@ -1431,7 +1434,7 @@ class CuraApplication(QtApplication):
 
         self._currently_loading_files.append(f)
         if extension in self._non_sliceable_extensions:
-            self.deleteAll()
+            self.deleteAll(only_selectable = False)
 
         job = ReadMeshJob(f)
         job.finished.connect(self._readMeshFinished)
diff --git a/plugins/CuraEngineBackend/CuraEngineBackend.py b/plugins/CuraEngineBackend/CuraEngineBackend.py
index 47f7a07b94..ea7440843e 100755
--- a/plugins/CuraEngineBackend/CuraEngineBackend.py
+++ b/plugins/CuraEngineBackend/CuraEngineBackend.py
@@ -426,11 +426,10 @@ class CuraEngineBackend(QObject, Backend):
         if not isinstance(source, SceneNode):
             return
 
-        # This case checks if the source node is a node that contains a GCode. In this case the
-        # cached layer data is removed so the previous data is not rendered - CURA-4821
+        # This case checks if the source node is a node that contains GCode. In this case the
+        # current layer data is removed so the previous data is not rendered - CURA-4821
         if source.callDecoration("isBlockSlicing") and source.callDecoration("getLayerData"):
-            if self._stored_optimized_layer_data:
-                del self._stored_optimized_layer_data[source.callDecoration("getBuildPlateNumber")]
+            self._stored_optimized_layer_data = {}
 
         build_plate_changed = set()
         source_build_plate_number = source.callDecoration("getBuildPlateNumber")