Was playing with two friends with no issues until we reached the Hive Mind level. At that point, from my point of view as host, all players left. From point of view of my friends, loading screen finishes loading and then kicked them from session. When we tried to set it up again, the same thing happened. 

One player notes they do not have Hive Mind unlocked, but that has not affected previous gameplay sessions. But it's notable in this case. 

If the game is gating levels behind personal unlocks, it should probably say that somewhere, instead of simply crashing the session.