I did almost exactly the same thing with an h1a, like yesterday. F13 host, 50.2 (6v). Worked perfectly as-is. I decided to swap the sense resistor. R025 swapped with R020. Voiala. Only high mode and double click to strobe.
No idea what I broke, so I ordered a few more drivers and a new set of 1206 resistors.
Nothing appeared to be grounded out.
High is decently hi. Just nothing lower. I think I got over 2k lumens, which is about right.
Funny to see the same glitch.
Broke my kaidomain c8 50.2 as well, same way, but that won’t come on at all. Got a driver inbound for her as well. I tried a r100 on top of the stock sense resistor on that light. No go… killed it. Now it rests in the drawer of lost hopes and dreams. Until new drivers come…
I ran the h1c in the same host for a little bit too. With a 35hi. Ran ok with 2 26350s, but not great with a 26650. I tailstanded it, one day, for like a half hour and it went out on it’s own. Apparently the led desoldered itself from the mcpcb. Went with the 50.2 after that and never went back. Now, I just need a new driver and maybe a OP reflector.
That shelf is really thin, and I blame that for the overheated hi.
So I turned the light on for a minute to let the step down timer do its thing, it only started slow flashing with no step down.
I had done this and other initial turn on without the reflector in to avoid a reflector to wire short.
I looked at both sides of the driver and there is no evidence of a short or anything burnt or other.
Yes it does look like the answer since the driver worked with your 12V XHP35.
The XHP50 has 4 electrical contacts on the bottom, unlike a typical LED (like XPL) which has only 2. If the XHP50 is soldered to a normal XM sized MCPCB the 2 contacts on each side are shorted which configures the dies in 2s2p, or 6V. But a 12V MCPCB has 4 contacts which line up with the XHP50 contacts, and this makes the dies 4s, or 12V. You can look up pictures of the LED footprints and it will make sense.
On mtnelectronics site, just choose the 12V option when you are buying the LED and it will come in the correct MCPCB.
In this case, with the 6V H1A and 12V H2C, they should be the same brightness because the 6V driver sends twice as much current as the 12V driver. In general it depends on the specifications of the driver.
Funner, what kind of 4S/“12V” XHP50 board are you using? Boards which make use of the emitter's thermal pad to connect the emitter's two 2S stages will not work correctly and I guess the problem you describe is exactly the symptom of such problem: the driver cannot regulate and goes “direct boost” over the upper 2S dices because the thermal pad is directly connected to battery cathode/negative terminal, sensing nothing over the current sense resistor (which is located between emitter's negative lead and ground). At least this is the way the H1-A driver works, a driver likely designed by the same fellows.