Kosis (Delirium boss) can teleport outside of his arena, softlocking Simulacrum.

Video: https://imgur.com/a/x9p0PCb

I think it teleported to a minion that was slightly out of bounds or something.

The Simulacrum walls in general are very buggy with their collision, because later when I ported out of the zone near the bottom (the portal was very close to the wall), the game snapped me to the other side into an inactive Delirium area. This subsequently caused my character to also become softlocked, and the game also gave a new wave window even though Kosis was still trapped two areas further above and it hadn't completed the previous wave. I noticed that if you dodge roll into some walls you can sometimes land on top of them and cast a portal there, which is probably not intended.