Had this same problem with my bumper. Had it painted 6 month ago due to an accident. Over the winter it started to bubble & chip.
I took it back to the shop & found out that they didn't strip the whole bumper back down before they painted it. Then they found out it had 3 coats of paint on it (1 from them & 2 coats from the factory). All those layers didn't help (the last 2 pics are the underside of the bumper- you can see the original paint still underneath).
This time I had them take it all the way down & do it right.
