I have a few locks that rotate a couple of degrees when I put them under tension before I even start picking. They're well used locks that have been out in the elements a bit so I'm guessing that's got to do with it. The problem is, I'm not sure what tension to put on these locks. When I apply a tension the plug rotates, then when I try the pins I have trouble setting them and I can't find one that's binding significantly. They're pretty cheap locks and I managed to pick the one by applying tension the other way (which doesn't cause the plug to rotate with tension alone), and then I just used a plug spinner.
Has anyone else encountered this type of thing, and if so what's going on with this initial plug rotation?