I had a gen 1 matrix that would do this periodically. If I remember correctly, there was a screw that was visible and another that was under the grip….which was actually the critical screw. I never tried anything beyond taking it apart, cleaning and re-torquing, to make it stop. I never let it get “loose” and never noticed a change in shooting but when I noticed a flex as I held it, I would take the grip off and tighten everything down. My pro II doesn’t seem to have the same problem.