I had issues with mine a few times after taking it apart and putting it back together.
The reflector was shorting out the leads on the LED board…I added a piece of insulation on top of the solder points and made sure the reflector cut-out was centered over them. That fixed it.
That might have been it. I’m not too worried but still I felt pretty stupid. I know better and usually pay more attention. I do like the light though. I might have to get another one someday and leave it stock. Well after putting some extra thermal grease down. The one I had barely had any at all. Three little dots was it. Might be nice for you to de-dome it. Get better throw for in the water anyway.
I’m using this one for underwater video, so I’d rather have max output possible in a wide area (not so much long throw).
That’s why I painted the reflector flat white. Gives me a much more even beam with few hotspots.
But, I know these XM-L2’s can produce much more light output than they currently do in this light and thats why I’m trying to mod it.
I’m not concerned much about runtimes either, as I typically do not have the light on for the whole dive, and usually just turn it on when recording something interesting.
I like the light as it is fairly compact/thin and has the mag switch for underwater.
Ive also taken it down to about 130 feet underwater, so far, without flooding.
I hope something can be done with this driver 
Thanks for looking into it!!