try this before spending $
My '98 328i does the same thing, the cover will not come up because the top is in its way. After you push the "top down" button and the top begins to go back, reach back and grab the top and gently pull it toward you. Once I pull the top, the cover releases and the top continues to go down. Your problem might be different, but it's worth a try. I have been doing this for 2 years, and it has made no difference whatsoever in the top. Good luck.