Simulacrum bug with loot dropping in the other room. 1,261,060,600

Doing a simulacrum, I believe i knocked back the boss into the previous room. Some loot dropped in my current room, some dropped in the previous room that I cannot enter.

Additionally there gives me the option to do wave 16/15... im going to try it now, I expect it will bug out... or maybe this is real?

Maybe this is the actual nightmare... i dont have access to my loot and I get additional waves?

Edit: Doesn't let me do wave 16/15