Thank you for posting your feedback. We are sorry to see your low star review on DAP Patch N Paint Lightweight Spackling Paste. Paint "flashing" can occur when the patch is painted prematurely (not fully surface skinned/surface dried), where lower quality/highly filled flat paints are applied (as is the case with ceiling paints) or where insufficient paint film thickness has been applied. Of note, the "sheen" that that you appear to be describing may not be "flashing", rather, it may be an artifact of applying a flat paint to a surface (the patching compound), which is likely smoother than the surround surfaces (previously flat painted surfaces. This issue as described, is almost always able to be corrected with the application of a second coat of paint. Should you have any additional questions, require further assistance, or wish to discuss this in more detail, please contact DAP’s Technical Customer Service Department at 888-327-8477.