Took my S2+ Tan with Biscotti apart last night and wanted to replace the GITD o-ring with a black one. So I installed the black one (which is much thicker and the pill screws in less than before) and when all back together the fit for my 18650 was pretty tight and light wouldn’t turn on. So i figured the end of the battery tube wasnt making contact due to the tight fit. Took head off, made sure tailcap was all the way down (it was) and reassembled. Same thing. I could turn on light when i unscrewed the head a little and it would come on and work fine, but all the way tight, nothing.
It also worked fine with a shorter cell with everything tight. So i put the GITD o-ring back in and all is well as before (completely screwed together, works with longest cells i have). So my question is, what causes a flashlight to stop working when all connections are tight but the cell is too long? Hope this makes sense, i’m just curious about it.