Don't ask me, I don't know either. I used it as normal on my M2 but of course I interchanged it a few times with the original M2 bezel so I could opt for incand and LED. I guess the screwing in and out sort of disconnected the spring from the soldering on the LED's wire.
The replacement KL3 they gave me had a very loose outer spring. I thought something is not quite right but did not question. After fixing the KL3 onto my M2, I couldn't remove it. The spring got caught onto my M2's interior casing. I had no choice but to use force to turn it out and that broke the spring, the interior of my M2 is full of scratches too. I sent the KL3 back to SF with the chippings of my M2 on it just to prove to them that it is a genuine problem.
Andy Ho