group chat disappear

[haraki-estic]

group chat disappeared all the sudden.

this happened to several group made by 4 specific members.

(4members,A,B,C,D. the disappeared groups were made by ABC,ACD,BCD)

the group chat disappeared in all member's chat room list.

when we search the contents, it sometimes comes back, but sometimes doesn't.

After coming back, it has only 1 month of chat history. Disappears again in few days.

I'm sure the rooms and the histories aren't deleted because they exist in the admin page on broswer.

Does anyone know something about this?