Paint/plastic crazing

I'm assuming that the top coat on the body was the same Rustoleum Gloss Black? I'm thinking a reaction with the primer and top coats used initially. I've got the same kit in Street Demons form (Panel Wagon) and didn't have any plastic / paint reactions. Lemme chew on this a bit and I'll get back your way lurch.

Glad to have you here BTW.

I am a little late to the party here but another possibility is this...Mold release agent...Yes the kit manufacturers use it to get the parts to fall out of the mold. Since this kit is an old release. It is possible that the release agent soaked into the plastic. At this point, no amount of scrubbing in the world will remove it. You do scrub all your parts before working with em/painting em right?? Dish soap and an old tooth brush works just fine for this. Once the plastic was exposed to the solvents in the paint/primer the release agent was revived and caused the reaction you experienced. It can and does also cause fish eyes and adhesion problems as well. I like to scrub old models with a good laundry detergent (without bleach in it) then sand the bodies with 1800 grit paper before doing anything else. Helps to mitigate contamination issues with old plastic. But, more often than not...Its the paint/primer. For starters, don't cross pollinate.(don't mix paint brands) krylon and rustoleum together is usually not a good combo. Different formulas. Rustoleum primer/rustoleum top coat. Same with almost any other (But not all) paint brands. In my experience, rustoleum primers are hot paints. They bite into the surface aggressively causing crazing of the plastic.(Especially if applied heavy or not allowed to dry properly between coats) Sorry, this is getting long winded, just want you to be well informed. Also, not letting the primer/paint flash off properly between coats will cause the crazing to happen. Too many coats too close together traps the solvents that are supposed to gass off/dry between coats. Those gasses have to go somewhere, they will bubble up through the paint layers (Looking like small craters/fish eyes) in the top surface coat or...Go the other way and attack/craze the plastic itself. I could go on for hours about paint troubles and what causes/cures em but. I will stop here and say that I feel your issues were two fold.
#1. Using two different paint brands on the same parts.
#2. Insufficient flash time
#3. Possible mold release agent contamination
Ok, maybe three fold. I hope this long winded litany helps you out. Best course of action. Do test panels with the primers/paints of choice for your project. (Cheap plastic spoons are perfect for this) Do try to stick to one brand for the top coat/finish products for your project. Last but not least (should probably be first) Develop a plan/routine for your paint sessions so that the environment and process are the same each time (or as close to it as you can manage) This will lessen the chance for unforeseen gremlins and ghosts in the machine to sabotage your paint jobs. Good luck!!