Update: I just tested it by opening a second window on the player page and leaving it in the background for 60 mins while I worked in the admin panel in another window and experienced something that is very similar to what you described.
If you leave an admin panel window/tab open but don't do anything in it for 60 mins then that window/tab will log itself out and drop back to the login page with no message. However, when it does the logout, it will also end any other session you have going - so if you are working in another admin panel window/tab then it will also expire and drop out to the login page when you eventually move between functions. It will give you the "your session has timed out" message. This is all by design.
I strongly suspect your log out issues are being caused by your open/idle admin panel pages/tabs timing-out after 60 mins of no activity.
For those reading along - my recommendation is to nothave open admin panel windows sit idle for 60 mins or you will be logged out of all windows. If you must have an open tab or window then click on it once every hour to keep it alive or close it once you have finished with it. [This 1 hour timeout was added to pages about 1 month back to support the multiuser match locking feature]
The page logouts on timeout was added around 1 month ago which roughly coincides with when you have been encountering these issues.
While I appreciate that having a second tab open is handy for adding players easily - you can still do it - just don't leave it open and idle for 60 mins. It just requires a single mouse click on the page somewhere to restart the idle timer.
I hope that helps.
PS - the idle timer serves a good purpose and it is there to support the match editing-lock feature for multiple users.
Update: I just tested it by opening a second window on the player page and leaving it in the background for 60 mins while I worked in the admin panel in another window and experienced something that is very similar to what you described.
If you leave an admin panel window/tab open but don't do anything in it for 60 mins then that window/tab will log itself out and drop back to the login page with no message. However, when it does the logout, it will also end any other session you have going - so if you are working in another admin panel window/tab then it will also expire and drop out to the login page when you eventually move between functions. It will give you the "your session has timed out" message. This is all by design.
I strongly suspect your log out issues are being caused by your open/idle admin panel pages/tabs timing-out after 60 mins of no activity.
For those reading along - my recommendation is to not have open admin panel windows sit idle for 60 mins or you will be logged out of all windows. If you must have an open tab or window then click on it once every hour to keep it alive or close it once you have finished with it. [This 1 hour timeout was added to pages about 1 month back to support the multiuser match locking feature]