I only use a 100% carnauba wax (Harly Wax) on my silver and grey UJ and black bonnet stripes as it doesn't contain silicones or abrasives. I personally wouldn't use any liquid waxes. If you use say Autoglym on the black stripes you will see it removing the ink
I noticed some peeps have been having problems with the silver vipers and UJ which is probably caused by strong UV sunlight so in the summer I use 303 Aerospace protectorant.
Sorry I didn't reply sooner. I have heard of this problem before where it seems to be the lighter silver parts of the UJ that seems to get these spots, you could try a mild wax like Autoglym after washing and see it it removes the spots, but don't rub hard as it will mark the vinyl. I hate to say it but as other peeps have said about a similar problem, it maybe the vinyl is starting to deteriorate. I'm not sure whether the vinyl BMW use is very resilient to sunlight UVs and general weathering and if the car if left outside all the time.
How long have you had your UJ? if it's less than 2 years I would see if the dealer will replace it as I think the warranty on their vinyls is only 2 years. Had mine on about 2 half years now and seems perfect but then I've used plenty or Carnauba wax on it and the car is always garaged and not used in bad weather or the winter months which I reckon has saved it upto now. I think if mine did deteriorate I will just get it removed and polish the roof up.
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