For about 6 months now my favorite pocket light, the S15R Olight, has been giving me trouble. Every so often it would not go into high mode, sometimes it would not go into Mid. It almost always worked okay in moonlite and always would run in low. Sometimes the light would flicker brighter, then remain in low. When this would happen I would sometimes remove and replace the battery; sometimes that would make it work again. There just did not seem to be any rhyme or reason. I would make plans to contact Olight. If I left it on the desk for a day or so it would start working. Intermittent issues like this can be a bear to solve.
Last night the S15R took another fit and only worked in ML or low. This AM it was still acting up. For some reason I decided to try the light with the tailcap from the S15, non rechargable, version I also have. Ta-Da!! The S15R ran through all the modes just fine. After switching back to the correct tailcap the S15R was back to ML and low only. The S15R tailcap on the S15 made the S15 malfunction just like the S15R had been doing. Hmmm.
I grabbed my spanner wrench and found I could turn the tailcap retaining ring about 1/4 of a turn tighter. With the tailcap replaced the S15R now works again through all functions.
Just thought I’d mention this in case anyone else has a similar problem.