I Have had this problem with my caps.
The way I solved the problem of the caps moving is to use a piece of double face 3/4 inch 3M tape cut in to two 1 inch sections. Then remove the offending cap put the two pieces of tape across from each other on the wheel in the area that the cover support tabs snap into this holds the cap in place and allows easy removal. The foam tape compresses and should not break the tab off when you push the cap back in place. It has worked for me.
