As being a spray painter for many years and now working for a leader of automotive coatings, the bubbleing issue could be an effect of many problems, addhesion, moisture and oil, dust under colour or even a reaction of from the devil himself "Polyester"...
It's very difficult for a painter to addmit his own fault, but an assessment by the right person should be able to give you a fair idea of what was the cause. One idea is by cutting the paint with a sharp razer blade and actually seeing where the last layer actually lets go. Haveing said that you would then have to paint that panel again, from this you will determain weither adhesion was the cause.
If you need anymore help send us a post,
Good luck.
Kustoms4u,