Priming and painting PVC?

We are making a special project, and we have to paint PVC pipe a metallic copper. We bought spray paint primer for plastic, let it dry overnight and then sprayed the metallic copper color over it, but it is ending up with this crackling over some of the areas and is no longer smooth! Why? We worked so hard on the construction of the (toy) we're making. Any ideas as to why this happened or what we could have done wrong. It didn't crackle everywhere, just some of the places. We may need to remake the special toy.