Got my Tangsfire C8 last month and I applied copper braid mod on both tailcap and driver end. Switch was working fine, till I re-opened it for GITD button upgrade. I got this intermittent blinking problem while performing my LUX test. I release and tighten my C8 but problem did not 100% go away.
Finally, I got some spare time today to troubleshoot this problem. I opened up the tail assembly and made a throughout inspection include connectivity test with MM.
I discovered my mistake and I made the illustration below to explain what actually happened.
The main cause of the problem, was due to the excess solder(abt 1.5mm spread) which formed at the edge of the spring. The extra height prevent the assembly to have good contact, with the switch’s PCB contact ring (RED). I suspect a gap was formed between alu block and switch’s PCB/ contact board(not sure about terminology) despite fully tightened.
Solution:
1) Relocated the lower copper braid end.
2) Clean up the excess solder and contact ring.
3) Conduct physical check of the assembly, before inserting into the host. Press it with your finger to ensure there is no gap in between.
4) Assemble the components and switch on and off your flashlight.
5) Shake and give it a light knock while it is ON. (stress test)
Hopefully, someone will find this piece of information helpful.