Thanks for sharing your experience joechina
I also had dim mode only, after using High mode, even on a fully charged battery.
imo the actual source of the problem is this screw (covered in solder), that is attached to the white wire (not the end we see on the LED board, but the other end), which is a ground:
To access it requires removing the LED board
Here is a similar screw next to the white wire, on the Mi1c, but it is accessible without disassembly because the LED board is cut away to reveal it.
Clemence told me the screw at the bottom end of the white wire, on a Utorch I sent him to swap LED, was very loose. imo when you and I have “fixed” the problem, by sliding the LED board around, we are jiggling the screw in a way that makes better contact, temporarily. My hunch is that the poor contact makes the light unable to move enough power to run high mode, and causes it to step down to moonlight. Just a guess.
My Utorch modded to SW45 9080 has been reliable since Texas Ace did something to anchor the white wire to the LED board with sugru, though that did not actually address the loose screw under the board, it seems to have stabilized the connection. He also mentioned that it seemed like the white wire may have been “shorting to the LED board”.
Due to this Assembly flaw (loose grounding screw), I am not recommending buying any more Utorch S1 Mini. I recommend the Klarus Mi1C instead. I like the lower moon level (0.2 lm) on the Utorch, better than the 1 lm moon on Klarus, but not the unreliability of the Utorch. I like the lower Medium mode on the Klarus 45 lumens (6.5 hours runtime), instead of 100 lumens on the Utorch (3.25 hour runtime). The Klarus has not had reports of failure like you and I have experienced with our Utorch.