We used to paint the roof on the minis white (Or any colour of the buyer's choice), we had a disaster with one, the customer complained that it had all gone as though covered in raindrops. Our paint guy stripped it of and did it again, same result after a couple of months the same complaint.
We asked the paint company for advice, they sent out a man, a little guy in a bowler hat, he inspected it and said "Your customer is washing the car with Surf baby detergent, it's the only chemical that will do this to the paint."
Sure enough the customer admitted that was what he was doing, thought if it was good enough for babies it must be ok for cars.
We stripped it of and did it again he changed to Deb car shampoo and all sorted.

Anyone who has never made a mistake has never tried anything new. (Albert Einstein)