<p>Hello all.<br> When I have my F3 set up for long exposures on occasion it will misfire. The camera is set on B. Cable release is attached. When I push in the cable release it will lock open as it should. I can hear the shutter open and then close after a second or two. I replaced the batteries and have used 3 different cable releases. I'm stumped. So, I humbly beg your help. Thanks in advance for any advice on this matter. </p>