Rain will do it. Cold will also do it if you have shaky solder joints, I have had this happen in past years. Replacing triacs and reheating solder joints has worked for me. I have one now that sometimes stays on after the show ends and sometimes not, but it seems to work great during a show. I have bigger (higher priority issues to work on so I've just left it for now. I do have a spare LE if gets really annoying to me, but I'm to lazy to even go out and unplug everything to put the spare LE in place. Replacing a triac is not difficult, but be sure to read some of the posts that talk about the best way to do. Some people remove the heatsink and some do not. I have always removed the heatsink just because it seems easier to get to the bad triac even though you should unsolder from the bottom of the board, but next time I do it I am going to try it without removing the heatsink. I have some better cutter now to cut the triac off at the legs before doing the unsoldering.