Hi Malcolm J, sounds like your Zorki would benefit enormously from a clean and service. All that grease will have been in there for that long too, only that could have stopped being a lubricant when flares went out. You can imagine, say, a delayed shutter operation causing the curtains to move more slowly than they should. Just for an example, say their speed across the aperture was 125th sec longer than it should be. So that the fast speeds would look to be very slow but the slowest speed, say 30th could now take around an extra 125th to operate, probably undetectable. Only the fastest speeds might look slow, in fact they may all be slow by a similar amount.
Only a possibility, of course.
