Piston problems are mostly to do with over-greasing and fat o-rings.
I've had several drivers killed, mostly by slipping with alligator clips while powering them to measure power draw and trying to switch modes at the same time. :facepalm: Some "faulty to start with D10s" I have managed to fix by replacing components on the driver (if you can figure out which is the problem through some tricky testing), and some times its just a hardware problem with people not installing light engines back together properly, however the biggest problem is with people sanding pistons irreversibly short, in an attempt to correct for a improperly installed light engine, and ending up with a torch that can no longer function, but gets advertised as a "mode changing problem" because the torch will still light up when the piston is pressed, but can't stay on. Id give a not quite working torch a go, but only if your keen to repair/mod and comfortable to get into it, because its more often than not, a complicated exercise, and can usually be more frustrating than its worth. If you get a good price, its worth a try.
The D10 is what I like to think of as a serviceable and moddable torch. D10s have the looks, D11 loses the elegance both UI and visually(to me..), D11.2 is fine tuned a bit, with improved UI, however its still not perfect IMO. All 3 are still fairly cool torches to be playing around with.
Ive got some D11.2s still siting in a box unused, and D10 users that I have which I've spent a lot of time just fine tuning. Emitter swaps are easy enough though, but requires attention to detail to ensure it fits together nicely, with the thickness of the led mounting base highly critical to the piston throw and feel.
