Not at all my area of pseudo expertise, but a couple of thoughts.
1) A couple of pictures might help get you the answer you are looking for on this one.
If this is the case of some sort of screw loosening under recoil, or a not so tight fitting dovetail -
2) Loc-Tite Threadlocker. They make a couple of different "levels" of toughness. Green, Blue & Red. Green is mild, Blue is medium and Red is hardcore.
Hope that helps!