Yes, some samples will develop this type of problem from time to time. I've noticed it on all my PD lights. All that is usually required is some cleaning and fresh lubing of the piston and the brass switching ring around the pill. Sometimes just a quick twist of one or the other will cure it for awhile. If this kind of routine maintenance is a problem for you, then this light may not be for you. :shrug:Yeah OK, so after my last post it all starts going downhill! Erratic switching, switching itself off and from high to low in no order It's been sent back to swap it for a Nitecore Extreme....Hopefully that will be better.