Ran into this on my aegis carbon frame. It had a moving shifter boss when I got it. After some research and a closer look, I sawThere was a tiny flathead screw in there. Some two part epoxy and some masking tape later and it hasn't moved in a thousand or so miles.

P.sure I found the part on loose screws or something like that. I know cannondale used two nuts on a length of threaded rod.