Sorted, been driving me nuts, as you know you insert key mine turned very stiff and then the barrel should receed into cylinder and tighten against frame of locker, well this was getting near impossible dispite covering everything in WD40 so i took both units off turned both upside down n poured bycicle chain lube down both ane let stand for a few hours, and hey presto they work like a dream both as smooth as silk, I think but maybe wrong thst the way they're angled rain must seep throgh the key entrance and fill l the chamber over time causing rust n gunge to build up over time, so no matter how much oil or WD40 is squirted in it doesn't seem to work, taking them out n turning upside down and the water just trickles out so after most of it is out I poured bike lube in and left fir an hour or so and it worked a treart, ( well thats my theory anyway and it worked )