What you describe is normally caused by a contaminated surface during repair, ie; improper cleaning, left over wax, silicones from the shop, water vapor in an airline, even an oily fingerprint. Another common source ia oil bypassing the rings of the compressor, while being painted.
Grinding out the repair before proper cleaning can actually force the contaminent into the "glass". I'll bet your body shop will go the extra mile to "disinfect" the area this time. Easy to miss on a "re-repair".
Some of the simplest repairs can be a shops biggest headache. Don't dump the car, I'll bet they get it right this time!
DV