Two players having each a mission in the same poi, was always a problem, once you've done the quest of one player, you can't start the quest of the other player until first player returned it to the trader.
I guess there is some wierd mixup between quests in multiplayer.
Today we figured out:
Player A had a nighttime-only quest in one POI while player B had a fetch quest in the same POI. Player B started the quest (which at the exclamation mark was told as fetch quest), but it turned out it started the nighttime quest of Player A. We had to repair a generator and there was no satchel. DURING DAY!
There is obviously something really strange happening with shared quests in the same POI. Is there some sort of single instance of quest per POI, instead of having two quests by each player?