MUCs, in roster, sometimes go in « not in roster » instead of « Chatrooms »
See screenshot
Sometimes, the minimized MUCs go in « not in roster », and are considered as normal contact, instead of MUC, so a right clic on it displays a menu as if they were contacts. (so, no « disconnect » possible) The main problem is that they are empty, can't be disconnected or reconnected, and I can't even talk in them.
The only solution I have is to relaunch gajim...
I will investigate on how and why this happens, but it's pretty often so I think it's critical...