I wonder if part of the problem was caused by intermittant/poor contact between the metal tailcap and the flashlight body. Glad you tackled the problem and your efforts paid off. See you on CPF.
I think that was the case in the CPF forum post. In my case it seemed to be mostly the switch contact. I was able to duplicate the issue with the switch part separate from the body of the light. Although there seems to be some degree of a continuity issue to the body as you need to get that switch end tightened just so to make it work.
Funny I had issue s . Fenix light.I loved it .fenix was so nice they sent me parts. Free. Yeahh . I gave up trying to fix after a month. They forgot to tell me. Manufacture a thing. Or hire a machine shop manufacture a thing to hold a thing in a clamp. Then try 25 steps after that. That I have no idea about . Man I was close to fixing it . I still have it. That’s been over 10 years( can I send it to you. I actually have. 2 Fenix light s now that don’t work) you can make cool video. ??