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Post #14 is right; My signature car's body panels are 75% composite, and I have polished them in the sunlight (not direct, however) a few times w/o issue.

Off the bat I would either suspect a defect in factory paint (it does happen!), a pad that could've went awry, a mishap, or a number of mysterious things if the OP is claiming that he/she did not do anything intentionally wrong.