My understanding as to why as told by a Chemist friend, is their addition of Paraffin Wax in the Base formula. I tested it 8 different ways from not sanding, sanding and tacking, sanding and wiping down with water rag, wiping down with water/soap rag, scotch padding etc. then recoating and clearing. In every instance where it was sanded and rebased and cleared when I took a piece of tape and pulled it delaminated at the rebase layer, just like the Chemist friend said it would. It went against everything DuPont and my Reps have said and always told me. When I did the test I was going to Training and I took that panel with me and threw it on his desk before class started and asked "can you explain this?" his reply was what I was told he would say "you must have done something wrong".
You can feel the wax in the mix. Do a test panel, scuff it and run your hand across it, it has a waxy feeling and nothing will stick. I was told that as it flashes off there is a micro layer that comes to the top allowing the next layer to adhere but will be removed when sanded exposing the wax under it and any additional layer of base or Clear will delaminate.
I brought it up to my paint jobber and after I explained what I did and asked what he knew, he said without me interjecting said "Paraffin wax?".