Maybe I’m the only one, but I found that when I load a game, for the first round in the arena, none of the mutators have chests assigned, with the exception of the “no mutator” option (which you can’t choose anyway). Kind of annoying since I quit to true or normal mode fairly often to use the grinder, since there’s no fast travel in the cortex.
Anyway, if anyone encounters this, I’ve found that if you quit with the quest completed, BUT NOT TURNED IN, you’ll have the chests to choose from when you come back, as normal.
EDIT: I’m on PC