After half an hour I managed to reproduce this bug. It might have to do with the bubbles. After one game maker update the bubbles often crashed the game. Before the update they worked perfectly fine for several years. After one week of work I found a workaround. But this bug is much more rare and if I try to fix this for another week ( I most likely can't fix it anyway) I will never be able to start making Bobo The Cat 2 (and I can't wait for that. In my mind Bobo 2 is already finished.). But your effort was not in vain, this is really interesting for me and important to know.
That's good to hear. But I have to say that it might still take some years. I will start from scratch and will have to learn c# and unity while making this game. And there are many complicated little mechanics that are not so obvious for the player like the culling-system.
If there were good chances that I could solve this bug with less than 20 hours of work I would do it because I am not sure if the bug is limited to that room. I think it can appear in all rooms of the watertemple that are accessible with the submarine.