I have noticed the following problem in recent battles. After the boss fight it is not possible to use the exit. You die immediately. This has happened to me the last three times in a row.
I always run back now, otherwise my thrall always returns to the main base.
Which is also a problem.
I don’t have a answer for dying on exit. But put down a bedroll and park your thrall next to it and then have it follow you in to the dungeon. They will return to your bedroll.