Does the back cap button go one from the hole at all?
Because I had a small problem with the back cap button recently. I did not have any air left on the tank, placed it on the marker, and air it up fast, then it popped out. I had a SLG 10 tho. Never had any problems with the asa, my self, so i don't know. Tell me if it helps, and you manage to fix it.