I picked this up from my own experience and a little help from the local shop. I was having trouble with marker bindings, the whole heel and brake peice was falling apart. I found that it is caused by the brake levers gettin pushed around from either the other ski (like in a cross) or hitting rails. An easy solution was the cut off the inside brake lever on each binding, left one on the right ski and right one on the left ski. That way the brake to brake interference is prevented and there is still a brake left to keep them from sliding away if they release.