UPDATE: I could reproduce the crashes, if they happen at scene change. Godot crashes without showing any error, the one I thought to be responsible was a red herring, so I assume it must be an unlogged bug.
I might have pinpointed the cause of the error in the cleanup code on scene change. I have updated the build accordingly, see: https://dermondhase.itch.io/8-colors-sentai/devlog/538042/solving-some-underhand...