Floquil cracking problem

I sprayed some Floquil acrylic on a test kit yesterday. The kit had a Tamiya lacquer coat that was sprayed on last month. I was comparing three colors for the blinking Zero color. My Golden acrylic brew and a batch of LifeColor tan went on just fine. The Floquil Concrete appeared to lay down with no problem and dried up just fine. The next day the Floquil had cracked badly. I've heard of this kind of thing happening with Future or a clear, but nothing went on top and the surface was in good shape. And we've got a three paint control group - everything went on a 48 scale P-38 wing in separate sections. I like Floquil paints a lot (engine and grimy black both belong in everyone's arsenal) and can't remember anything ugly happening before. The stuff does dry fast - I've always got a damp paint brush ready when using Floquil to swab the tip. Anyone have any ideas? I've got a dozen bottles of the stuff and certainly intended to use them. But I'm sure glad this was on a test.

Eric