The new leicaflex I just got for free seems to have a sticky mirror. Any tips on how I might fix it? I got 21,35,50 and 135 lenses with it so is like to play with it but it sticks most of the time on slow speeds then if I bump it up to 2000 it immediately unsticking. A cla is $185 but I'm not sure I want to put they into the body when I'm halfway thinking I might just sell off the lenses at some point.