Pugsy: that paint and materials you used are compatible, ppg guarantees their paint and materials call a tech they will come out and look at the vehicle and may tell you what happened! or take a sample and Analise it! You tell them the procedures you used! and they will replace or refund!!! Call and give them the codes off the cans there may have been a call back on something and it was missed at the warehouse or jobber! Call PPG direct! dont go through the jobber.
Ditzler (PPG) is one of my favorite products and what happened to you is way out of the ordinary range of problems. If you sanded with 400 or 600 the paint should have bit and held, unless you sanded while the material was still chemically active (not fully cured) and the sand scratches shrank! or some kind of contaminant was between your material and color coat like a particular soap residue Found in some soaps from washing that a wipe (grease and wax remover) wont remove!!!
I would really be interested in what the tech finds! I would hate it to happen to me!!