I have an old Nikkomat EL which I recently picked up. It does have an unusual problem occasionally. About 70% of the time, after I cranked the film advance, I depress the shutter and nothing happens. Instead, I have to squeeze the Depth-of-Field preview button (sometimes quite tightly) and then it snaps (without pressing the shutter). This happens more so with film inside and in 'A' mode.
If anybody knows wat might be wrong, your help will be much appreciated