Originally posted by JBemus The battery was mentioned. One problem I've had like this was when using alkaline 6V batteries in the 6x7. They just don't seem to provide enough current to operate consistently. I've never had problems with lithium or silver oxide.
A lithium battery is not really a good choice in any of the Pentax 6x7 / 67 bodies. A very steep death dive that occurs suddenly can actually leave shutter and mirror activation in limbo. This is well documented and known to cause serious jamming of many auto wind-on cameras that
can take lithium but do not relay the correct battery-level state, and are thus predisposed to unexpected events — jamming, incomplete shutter travel, mirror paralysis.... Silver oxide batteries are the ones recommended in the Pentax 6x7 and 67 bodies, or the alkaline alternative, and there should be no issues with either type. A sticky solenoid could well be the problem, but this necessitates disassembly of the camera to get to the solenoid on the right side of the mirror box (viewed from behind camera). Long periods of inactivity can lead to this sticky solenoid problem, rather than reasonably constant use and age is a factor in many instances involving the early 6x7 bodies.