There are several questions that need to be answered first. Are these star bursts visible before the powder is cured? Is the wrinkle created chemically in the curing process or does the powder have some kind of filler that mechanically creates the wrinkle? Are you getting what the industry calls a "fish eye"? Have you taken a sample of the material and sprayed it in a different environment to see if the star burst problem continues? Answers to these questions will provide more information helping to answer your question. One thing that we know is star burst defects can be created from excessive voltage, inadequate grounding on the part, and chemical makeup of the powder or foreign material. Location of the gun to the part (target distance) affects how quickly the star burst effect (or back-ionization) will occur. The closer a gun gets to a part, the faster back-ionization occurs.
Back-ionization occurs when charged powder particles cannot find a ground point on the surface of the part and consequently build unevenly onto other particles on the part surface. As the powder builds, it insulates the grounded surface, resulting in a rough surface texture (in the uncured state). Typically called "starring," the uneven coverage of the powder will still cure, but produce an "orange peel" look. For most decorative appearances, the orange peel appearance is undesirable. Beside heavy film builds, excessively "hot" or conductive powders also cause back-ionization.