Not sure what happened to the thread starter, but thanks for not getting offended.
I don't know about this Ditzler Rep. DP40 is an epoxy and even when it was called DP40 (now it's DP40LF...the LF stands for lead free) should not have needed to be sanded. It should have a 72 hour window before you need to scuff it or open it for mechanical adhesion, anytime in that window and at about 70 degrees you can top coat it without scuffing. I firmly believe that if a vehicle is prepped properly, sealer isn't required.
You mentioned that you chemically stripped the deck lid and dried it...did you rough up the metal with the DA before you put the DP40 on? If you didn't, you could have had some residue left from the chemical stripper that could cause oxidization (same type of reaction as rust) and cause lifting.
Do you remember how long after painting it took for the bubbles to show up? If it was traces of chemical stripper on the panel the reaction would be fairly quick...if it took a while like the thread starter (his took a year and that's why I say it's moisture causing rust) then it wouldn't be the stripper.
The way I would have done the job would be to strip the panel, do my body work, 2 medium wet coats of DP40, let the DP40 flash, 2 to 3 coats of primer, (I would only use 2K primer up until recently), let the primer cure, block sand and paint. I would not have gone bare metal, body work, light coat of DP40, scuff and paint. Did the body work areas ever sink?