Hi, sorry about this issue. Are you using Google Account to log in? Currently there is an issue affecting certain Google accounts that I have not been able to fix yet. A work-around for this is to go to OGS’s Account Setting and set a password then use that to login (or link another Social account then use that account to log in).
There is no way to “prune” a branch yet. But this is simple to implement so I will try to add it in one of the coming releases.
Next time it happens you can wait for 3 hours to find out 
. I have seen games with no time limits timed out before, so I guess there is some hidden limit even when you cannot see it.