It is likely to be a problem with the clear coat, but you need to consult a paint specialist to determine the exact cause of the problem. It's quite common with cars of that vintage. I'm not surprised ...

My 2004 Toyota Camry Sportivo is in immaculate condition, except for the clear coat on the rear spoiler, which has begun to bubble and peel. I bought the car new and it has always been garaged at home ...