That's a head scratcher. But before anybody can answer of any worth, you need to do some careful observarton as to why the lens mounts so tightly. Was the lens dropped and the bayonet bent ever so slightly? Obviously it has the camera resistor out of contact, resulting in no reading. Establish trust with the camera that behaves best, then proceed to the other one. Too many irons in the fire means some calves will heal their too-cool brand so that a rustler can re-brand them.