I recently bought a Fenix MC10 anglehead light, and I have noticed a small chirp when I switch between levels. Sometimes the sound remains for a few seconds after I first switch it on. I also get the impression that the noise sometimes occurs if the light is bumped slightly. Is this anything to be concerned about? I bought two, and the other one has a bad flickering problem on high (and yes, I tried cleaning all contacts with alcohol) - it also makes the same noise, but only instantly when you switch to high. I am about to return the flickering one to the seller, and I am wondering if I should return the one making the occasional chirp as well. Any thoughts?