Definately switch out the 4 LR44 batteries, Bronica did specify alkaline, don't substitute for lithium. The shutter is electromagnetically controlled to hold it open; if the batteries sag, especially in the cold, then the sutter will close too fast. If the batteries are bad then it will only fire at top speed 1/500. If you have a motor drive then the drive supplies the power. It must be removed to check the small batteries.