Hi!
I just answered a fellow that had color seperation issues and he's apparently close to finished. This is a pain, I know. I have found that this can happen to the best of us at the worst times. Just when we think DONE! This problem raises it's ugly head!
How do we prevent it? Well, there's keeping the primed object covered for at least twelve hours longer than we would with filtered air circulation. Or Using a different type of paint. This is one of the reactions I have experienced with Acrylics!
I find that if you prime with regular enamel paint, then overcoat with acrylics you're gonna get hit with this, or sometimes it can be just the opposite. Sometimes the wrong kind of thinner, retarder or just plain differences in paint Batches can cause this.
I had this problem with Humbrol Enamel one time. After stripping the model twice, I got Peeved and just rubbed the finish( Bare plastic, with Denatured Alcohol) After the alcohol gassed out, Repainted, and no problem. Sometimes it is something in the formulation of that plastic ( Like it's a new run) and it picked up Machine and Mold lube in the hot mix. It would not necessarily show til paint or glue is applied!
Many folks espouse washing and air drying parts in a dust free environment, Before Painting. I cannot do more than say I agree one hundred percent!