The shutter in my Nikon F2 seems to fail every 20 rolls or so. It will work fine for some time and then I'll get a roll where it will not fire at all (blank areas of film) for about half the roll. Yesterday, I shot three rolls at a 9-11 memorial. The last roll I shot, a roll of Tri-X look fine. One of the other two rolls (both of which were Acros 100) only half the roll was exposed. So I know that the shutter began working again after this Acros roll was shot. The third roll I will develop tonight. Does anyone think it may need a minor adjustment or a complete overhaul? I'd just like some info before dropping it off to be looked at. Thanks.