Corrupted Nexus Map Bugged | Hidden Grotto

Playing coop, my partner got locked out of boss arena with no way in, first boss stopped moving/attacking 3/4 of the way through the fight. My Partymate dies for no reason while being locked out of arena.

I died during second boss from getting stuck and glitching. Respawned the whole party and the first boss wouldn't respawn, the map says "map completed," so we exited the map to find that the area had been purified despite not beating the second boss. My quest tracker still says "travel to corrupted nexus"