Alright, I realized what’s going on. each of these rooms is encompassed by a box trigger that hides everything inside the rooms where the actor is not.
some kind of actor that manages particle emitter must be spawning at 0,0,0 which would be inside the big Y room’s trigger box, so when I’m in the box it gets unhidden, and when I leave it’s hidden again.
I can’t figure out what kind of actor is being hidden, so I can exclude it from the hid classes. I thought it was a particle event manager, but unhiding every actor of that class didn’t fix it.