That's a terrible feeling when something like this happens
; I've been there! Like the other replies if your going to get help you need to tell what products & what procedure you used. From experience and advise from PPG that we received - you need to 'seal' before laying down the the color. This could be what happened if didn't you seal the primer surfacer before painting. It could be that the color was so hot (chemically) that it burned right into your surfacers and body filler and then trapped moisture under the surface. If you haven't solved the problem yet, as I see it the only way is to find out. Would be to first lay down a strip of masking tape on all four side of the bubble and shave it off with a razor blade. Then let the viewers know 1)what you see, 2) what products you use maybe then someone can give you hand in where to go next. Just so you know I am not current on todays 2 stage products, only experience is with one stage and sealing with with DP-40 before paint.