It seems that about 1 out of 3 pieces I make lightening holes in warp when I flange the hole. Nice flat piece suddenly has a bad warp and twist. I’ve done dies, rubber sheet in press, the wheel thing you spin around the hole and a good old stick. Doesn’t seem to matter how I form the flange the same thing happens. I can make several identical pieces and one always seems to turn into a potatoe chip. I can usually work this warp out, but not always. Can’t seem to figure out why this sometimes happens and other times it doesn’t. I searched and wasn’t finding much. Any insight appreciated.