My guess is it has to do with too thinly sanded original 2k or the original paint, and absorbtion or solvent attack. A place I worked at wiped down some parts with mineral spirits, its not real aggresive, but also doesn't do a good job removing contaminates from the surface. But painting over a surface that is wiped down with mineral spirits itself I haven't seen to be a problems, if the surface happens to be free of contaminates and the mineral spirits has been able to evaporate. I am not real sure on this one, but believe that a sensitive 1k finish or thinly cut primer is the root of the cause based on information so far. Why it didn't do it the first time if the paint you applied over is the reason is beyond me, unless the first coat happened to be applied dryer then this time. Or unless the cause is contaminates picked up, the mineral sprits or some problem with the original primer somehow. Is this actually blistering-like swelled bubbles, or is it lifting like crows feet.
Paint defect causes for blistering listed by ppg is
Cause
Moisture or contaminants trapped under the surface. This may result from:
a) Inadequate surface cleaning, leaving residual moisture or contaminants such as oil, industrial pollutants or grease from finger tips.
b) Incompatible materials or the use of non-recommended thinners.
c) Insufficient thickness of paint leading to increased permeability.
d) Water permeating both newly applied and aged films. Exposure to rain or high humidity before the finish is fully hardened increases the risk of blisters caused by permeation.
I think to rectify I'd sand out all the blisters and wait till you can get a better contiminate remover, and be sure to follow wiping on with a clean dry rag and allow a lot of time for that to evaporate before thinking of priming. Then don't hammer on the new primer coats, lots of flash time between. Somethingis getting trapped, you have contaminates or a sensitive surface.
