made a try to somewhat fix the problem however cannot test it is gone.
Would you check if bubble problem still persists?
Viewing post in WithoutCowboy jam comments
Managed to reproduce it, although not with the first scene but with the second one.
There is something fishy going on with the pool of scene bubbles and I'm not really sure Godot behaves correctly, it might be an engine bug.
For example I've seen there residual things that are not nulls but also not sth else which is really weird.