I’ve cleaned the contacts, opened the switch, tightened. There is a flicker when turning ON with a NiMH. On a 14500 it is perfect. I guess the NiMH is shorter. Is there a fix for this? A paperclip didnt seem to give any results.
maybe add a battery magnet spacer to the NiMH -B ?
How much shorter is it than the 14500?
You could just pull and stretch the -B spring.
I would not use anything on the +B, it could slide around and short +B to the battery tube.
If kramer5150's suggestion doesn't work, I would contact Thrunite. In the past, they have been very good with customer product resolutions. Getting to the driver without damaging that light is tricky as it probably has Red Loctite like mine. If you do get to it, it's a sophisticated driver that will require some deep electronics knowledge to diagnose. This is just 3 of it's 7 inner component surfaces:
