I learned something the other day...
I stripped the paint off a body with CSC and the only place the primer really stuck was on the places I had done body work (filled and sanded).
So, on my next project I sanded the body with some very fine sandpaper (1600) before priming.
Your problem may be due to mold release left on the body or even due to body oils from handling the parts before painting.
You've already tried to re-coat the parts, so stripping or sanding to bare plastic is the only thing I would try.
