Webb and Noah may be right, but I doubt it. Chances are the kerf sides aren't touching, and if they are not, then simply tightening the bolt will do it. If the kerf is bottomed out then you will have to widen it, but don't do this unless you have to.
The UHMW blocks do wear over time and eventually you might have to widen the cut, but with the amount of hours on that particular plane, I seriously doubt it.
Always check the simple, cheap stuff first.