If the clear is oxidized below the topmost surface layer then the only answer is; sand, seal and re-coat.

Post up a picture of the trouble area and maybe we can give a better answer.

One thing I can tell you is that if the problem is the most obvious on the flat horizontal surfaces and not on the sides then the clear coat is shot.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now