New M645 user here. I received a used (but in excellent condition M645) the other day, and after I replaced the battery on the bottom of the camera, everything seemed to be in working order. I loaded the film and shot the first roll. However, I noticed that after each time I pressed the shutter, I had to press the little red power button (battery check button) afterwards in order to get it to allow me to advance to the next shot. Is this normal? It appears like the mirror is locking in the up position. Should I try replacing the new battery with another new battery? It's been ages since I shot a camera like this, and I can't find a mention of needing to do this in the manual. I also double-checked to make sure that I didn't have the mirror lockup or multi exposure on (and I didn't). All the shots were done with the metered prism. I didn't test the waist level prism. I shot the whole roll in hopes that this was normal, but I won't know for a week until it is developed. I know it's a long shot, but I thought there still might be some medium format users here. Anyone with thoughts on this?