The final_obj is the same object which the butil.delete command will …

…delete all meshes. This creates later an error. You have to copy the object

infinigen/assets/static_assets/utils.py

@@ -55,7 +55,7 @@ def process_object(obj, parent=None):
     bpy.context.view_layer.objects.active = mesh_objects[0]
     bpy.ops.object.join()
 
-    final_obj = bpy.context.active_object
+    final_obj = bpy.context.active_object.copy()
 
     butil.delete(list(butil.iter_object_tree(root_obj)))