When I changed the strut bearings on mine the top spring cup had worn quite badly and the hole was noticeably oval. This could well cause a clonk if the bearing can move around and will probably take out the bearing in time as well. I had to get replacements at a main dealer, at VW they cost about 25 quid for the pair which is a lot considering they're just two bits of stamped steel but had to be changed nonetheless
