I had a very similar problem with a Gerber AAA LED. I actually retired it because I thought it was totally dead. Then one day I picked it up and it came right on. Hmmm. Not sure what the problem is, like you I tried cleaning, battery and all that. I do not consider it reliable and no longer carry it.
I have Peak Matterhorn AAA and it has been fllawless. I plan to buy a few more soon. A great little light, I have the extra power version. Cheers