DRR reducer is a pretty harsh reducer, and 2 days Air Dry of the DCC and cut open with 600 really let the DRR reducer penetrate the DCC therefore lifting.
May I ask why you reduced it 100%, DBU is mixed 50/50 I think with the extra reducer alowed deeper penetration.

1200/1500 grit would of been alright to sand with and it might not of let the reducer to penetrate so deep, and still allow good BITE of the DBU.
Lighter coats of DBU reduced 50/50 with 15 min. flash time between coats . most likely would of stopped the lifting.

Its not that you did it wrong, as any freshly painted product has the possability of lifting.
I have had DBU lift itself in the summer when 2 toning a truck. Paint can be a crazy animal at times.


Spray