Definately not your tranny moving around, you would have more than trim moving if that were the case.
There are pop pin type things that are around tthe edge of the whole black bezel. I think theres like 3 on each side or something. What often happens is the pins break or the holes in the vinyl rip through. I would say take off the shift lever (its easy, pop the top cap off, take off nut, and pull off handle). then take the whole trim/slider assembly out, then put glue around the inside edge where it touches and put it down and be done with it. At least thats what I would do.
