Yesterday i found out that my Pentax 6x7 got some problems with slow shutter speeds from 1/125 and over, the shutter and the mirror stucks open forever. Like this: So i found a not so well explained solution online and this is my guide: 1- Gently remove the leather from the left side (the side with the 6x7 print) 2- Uscrew the 2 circled screws DO NOT UNSCREW THE THIRD. 3- Unscrew the two circled screws inside the focusing screen zone 4-Gently remove the piece by pushing it up and forward 5- Unscrew the two screws 6- Remove the piece 7- Cock the shutter, remove the battery and shot to open the contact of the magnet and clean it easier. 8- Clean the contacts with a small tissue paper wet with some contact cleaning detergent sticked to a thin screwdriver to reach every zone. 9- Test 10- Close everything 11- Stick back the leather This would solve your problem, hope that helps!