https://prosody.im/doc/modules/mod_muc

Limit on number of rooms in-memory
Prosody keeps recently active rooms cached in memory for faster access. The size of this cache defaults to 100 rooms and can be configured like this:

muc_room_cache_size = 100 -- the default
When a room is pushed out of this cache by other more recently active rooms, its complete state is serialized to storage and removed from memory.

Public servers may want to monitor and possibly increase this setting if rooms are moved in and out of memory very often.

When room is serialized to storage, room.jicofo_lock is not saved.
https://github.com/bjc/prosody/blob/master/plugins/muc/muc.lib.lua#L1671-L1675

When the room is activated again, jicofo_lock is null and remains locked.

I fixed to save jicofo_lock.