Simple Error Reproduction Project

20260812_005536.mp4

Steps to replicate:

1. Open main.tscn in editor.
2. Set the up_target on the PhantomCamera3D node to another node.
3. Change to another scene on editor (even a blank one)
4. Return to main.tscn in editor. The up_target is now null.

Removing the tool script from the scene root has the same effect.