Yeup, I agree , james, the locking ring is ELAs "Achilles" heel. It gets very , very dirty. Im my case I have to clean it daily. I dont know why mine get so dirty. Probably from heavy usage, I mean heavy. I change out batteries so many times a day. I go thru 16 mls a day, at least. When I use mine in the 350 mode, it performs much better. I cant figure out why, maybe my tele tube is wearing? I can see a mark where the locking ring sits when in 490/500 mode. Ive been using my first one for almost a year ( 9 months)