There are a lot of theories out there but the best Idea, in my opinion is to change out the the thumb screw and the set screws when all this starts to happen, as to start sanding and forcing the set screw harder and harder only starts the clamp itself to spread and then before you know it, you have to replace the entire unit. If one changes the set screw and thumb screw when all this starts, one saves further frustrations and money to do as I suggest above right away. Just my opinion and I works for me
Dick
heppnerguy