It was from cast lube. When I shoot cast everything gets caked. I shot 250 rounds. Did not clean. Was stored dirty in a frozen car. Went from frozen car to slapping a mag in with no check. Normally I don't leave the trigger depressed but I must have this time.
When I cleaned it you would not believe all the crap in the firing pin channel. Took a half doz q tips with hoppes to get it clean. I know the firing pin was froze in place that caused it. Glock 20. It was 100% my fault. Good thing I always point in a safe direction.