i think tank trials back button should be removed... there are so many people abusing it.
they would go alone in a room and would try to find his alt or someone to battle with, and if they fail to be with them they will use back button.
and that would leave the unlucky opponent/team without a chest.
I have been a victim of this kind of rude act... the bad thing is; sometimes u wont see who did that to you.