The reason for this bug is that the login timer window is still open, just not visible (which is also why pressing ESC will disconnect you back to main menu, as it's the same as clicking CANCEL during the login timer). I've had for the longest time a hacky workaround for this in 3_Game that just automatically closes the hidden login timer (by modding DayZGame::CancelLoginTimeCountdown, calling the super, checking afterwards if there is still a LoginTimeBase instance, closing it, then manually unlocking controls). It would be nice if this were fixed properly in vanilla, among the OnPlayerLoaded/OnRespawnEvent timing bug (it's basically chance if OnPlayerLoaded gets called before or after OnRespawnEvent is received on client, which means the respawn timer countdown window may be closed prematurely before the countdown ends).