I have a tandem trailer with surge brakes. One wheel was getting hot, so I jacked it up and found that it turned hard because a brake shoe was rubbing. I adjusted the shoes in, put it all back together and it turned fine. After a trip to the lake, it was hot again. I jacked it up and it was rubbing again. Took it apart and adjusted the shoes as far as they would go closed. Put it together and it turned great with no rub. Went to the lake, got hot again, jacked it up and the brake is rubbing again. What do I do?