Why do my LED lights flash on cold start?
I know this is an old thread, but I recently had this problem myself. Ended up being because of cheap bulbs. I have two of the same dimmers, one works fine, the other would flash once every time before turning on. I had just bought some "dimmable" LED bulbs on sale from Home Depot, and when I switched the bulbs for the LED bulbs I had in my other fixture the problem was solved. Guess not all dimmable bulbs are made equal. Hope this helps someone.