I just pressed play camera path and this happened (ignore the pause menu that's just obs being weird).
After this it just crashed.
I don't have logs cause of MultiMC stopped watching the game log because the log length surpassed 100000 lines.... and the last log was a hour ago..
At least replay mod recovers it, but still it should not happen.

Could you please attach that exact replay file so I can try to reproduce it? (you might have to change the extension to zip for github to allow it)

It doesn't happen anymore, but as you can see for some reason the play button isn't synced with the play camera path button. Maybe someone else will find a way to recreate it somehow.