I am going to take a guess that the area where the paint is blistering has some mold release residue or something on it. Oil based and wax based mold release agents will cause paint to blister or peel like that. Even oily sweaty fingerprints will cause it.
I would recommend lighty sanding down the area once again to remove all paint or primer and wipe down the area with something like windex or rubbing alcohol to remove any oily residue that might be there.
I have built many resin model kits over the years and have run into this a few times. I have also used a mild abrasive cleanser like Comet cleanser to clean parts before painting.
Also allow at least a day between coats of paint so it can properly dry.
Hope that helps ya. 