has never stopped for me while i still had quests to do. to go around this i used to refresh the game after i was done with questing. otherwise after i leave arena and click on train it would send me with the 'train button' then to the quests. i think the bug is related with the activity bar and that it is "moving" to the left or right when you go arena, HR, etc so you cant do certain things in some locations.
i think at some point the 'battle' button moves over the 'train' button and gets "stuck" there and thats whats causing you to get teleported back into the quest area when you try to click train.
stanly told me he is "aware" of the problem, that was a year ago ... good for him.