Kosis can jump out of area in Simulacrum

On wave 10/15, in the "field" region, Kosis can jump out of "bounds" (ie: to another blocked off region) of the fight arena, resulting in him being untargetable and thus unkillable.

sometimes you can be lucky and he jumps back, other times you have to restart the whole 150splinter encounter as he might be too far away to target you and this refuses to jump back.

After I passed wave 15, loot spawns in another room, it is impossible to go there. And the NPC offers me to pass wave 16)

both things happend to me not one time, wtf