Started a co-op game with 2 friends:
Bunker (Host) on 3rd quest, kill 300 bots.
Me as Zed on 1st quest, complete first zone without losing a generator.
Shroom on 1st quest, completing Devotion Garden first zone with Zed in squad.
We were having a regular run, cleared zone 1, I completed my quest but Shroom didn't (we didn't know at the time, he said complete Devotion Garden but wiki says zone 1, he should've completed it).
When we finished the second zone (Bunker finished his 300 bot kills), we went into the elevator, but Crystal Bot just walked out before host could pick between Procedural Factory and Labor Colony. We couldn't move or select a destination, host interface just disappeared. We were stuck in the elevator for a while, until host pressed Esc and "Quit to main menu". He loaded back into the game and could pick Procedural Factory as the destination. Once me (Zed) and Shroom loaded back in, we continued game just fine. My quest was complete, Host (Bunker) quest was complete, Shroom wasn't. Once we killed Shelldiver, I even got a second "Quest complete" message.
Once run was over, we went back to Saloon and noticed that, Bunker had 3 quests complete but only 2 chip slots, and I had 2 quests completed but only 1 chip slot.
Just finished a 3 person multi-player game.
Killing Shelldiver the two guests had finshed a mission (Zed kill shelldiver, Bunker 300 robot kills).
Middle of first zone floor three the game crashed to desktop for all three of us. The Host claimed he fully crashed, for me it looked like an ended process.
We reloaded the game and continued, ending up losing the last bossfight. When we returned to the saloon, both my friend and I (the guests), had progressed the library entry for our hero and could read the next quest, but the hero chip slot was not awarded.