Fix push free. CURA-4525

cura/PlatformPhysics.py

@@ -80,7 +80,7 @@ class PlatformPhysics:
                 # Check for collisions between convex hulls
                 for other_node in BreadthFirstIterator(root):
                     # Ignore root, ourselves and anything that is not a normal SceneNode.
-                    if other_node is root or type(other_node) is not SceneNode or other_node is node:
+                    if other_node is root or not issubclass(type(other_node), SceneNode) or other_node is node:
                         continue
                     
                     # Ignore collisions of a group with it's own children