Having a devil of a time keeping the vibrator arm on my P22 in place during gigs. It inevitably wiggles out and falls on the floor. I do remove it when I put the guitar in the case (to keep it from depressing the strings). But I assume everyone does that. So why does this thing keep sliding out ... and more importantly, what can I do to make it stay put, when I slide it in there? (Yeah, I know, "That's what she said...").