I have one SL150 steady front light, and an SL100 blinky in back. The reason I don't have two SL150s is that the back one broke and I ordered a replacement and decided I wanted a blinky back light.

I dissasembled the old SL150 light and found that there is this itty bitty wire that makes the whole thing work. It busted, probably on a jarring pothole or something, I'm not sure. I gave it to a professional electronics tech to fix. She did a good job, but it didn't take too long for the thing to break again. It did the same thing yours did.

I didn't try to return it because I'd had it for more than a year in hard condition use. I've had good luck with the front light, and the replacement is working great. Best of luck.