There was an issue on older projects where it was possible to corrupt the scene. I’m not sure if these assets were from before that time or not.
If you are using Violentmonkey, it is possible to corrupt the scene if there is a mismatch between the parent and children data on what exists/doesn’t
There is a fix available that is mentioned in this thread: Cannot find child entity of parent "Root" - Editor error, can't delete entities
There are also more detailed steps in the later replies using the Editor API