arctic dock
It can happen more than once in a single run, the other day i was in a bathroom (floor 7/13) collecting items and someone joined, for him the bathroom door was closed and he couldn't get out so i had to kill him with molotovs, the next floor one of the teammates went ahead and he triggered a part where the zombies slams and drop a door but only for him, when we arrive at that door it was closed for the 3 of us... i was the host, everyone left and i had to quit to main menu... 1 hour wasted.
The reward room door with the key card always close itself for the host at least once every run, i always let other enter first and open the chest so i can enter backwards always facing the door and jump between the table and the chest, then tilt a little my camera down to be able to pick the reward gun and ammo.
I hope this gets patched soon as it is and old bug.
(I have never experienced this while playing by myself)
wanton sinew