Got this guy in the mail yesterday. Tried it outside and it worked fine. Once inside in a room with zero light I noticed a very very faint light coming from the led while it is turned off. If I unscrew the tail cap this faint light goes out. Tighten it back up and it comes back on. This happens with various unprotected 18650s. This also happens with the protected 18650 it came with but it’s even fainter.
It’s so pale that I have no problem looking directly at it in the dark. Must be a fraction of a lumen. I noticed it’s only coming from one of the four sections of the led too.
Also noticed that if the battery is low this doesn’t happen. I think it was about 3.2-3.3v no load when I stopped noticing.