Could have crud or bugs in the pilot gas tube. They seem to like to crawl into propane pipes. Maybe take a blow torch and clean off the thermocouple in case there is grease or carbon built up on it. Or clean thermocouple with paper. Make sure there isn't a draft blowing the flame away from the thermocouple .
Discussion
I guess I'll have to give that a shot.
I don't have time to take everything apart again this weekend, so that'll have to be a next-weekend thing.