Jetbeam RRT-0 warranty questions

I purchased a like new Jetbeam RRT-0 a couple of months ago from a fellow member. The light would sometimes not go full brightness until you switched it on a dozen times or so. It would flash on high for a split second then revert to medium or so mode. It now won't even turn on usually unless you warm it up for a bit. Once it is very warm, it functions as it should. Any possible quick fixes? If not, is there anywhere I can send it to for warranty repair even though I didn't buy it from an actual dealer?

Have you tried the usual fixes?
Tighten the retaining ring on the tailcap.
Clean all contact areas including the threads, and relube the threads.
I used to carry the RRT-0 for a long time, and with regular maintenance that light worked forever even dropping it on concrete several times.