I kept having paint reactions on my boot lid, only way it was sorted in the end was to bare metal it, but think you may be able to get a sealer sprayed on now before primer to stop it coming back through.
Surely tho if the last place you used knew that was why you was having it redone would of done it properly, and although its sort of not there fault they should still have to sort it out. If nothing can be arranged then small claims court maybe