Rattle While Driving
We have experienced the same rattle you have described. At 3,686 miles our Buick dealer replaced roof mechanism brackets on both right and left sides. They checked with the Buick tech line for advice on how to solve the problem. I asked to see the brackets removed and saw that there is a small roller on each one. The parts manager pointed out flat spots on the rollers that they believe caused the noise.
The rattle was gone, but reappeared at 7,810 miles. Once again the same brackets( part # 133967030) have been replaced and we are now at 10,300 miles and the roof is quite.
Probably, until Opel redesigns this part, the rattles will reoccur.