Hello;
I would think that the lens was serviced at some point and the helical was not correctly ajusted. To check this, focus on an object about 1/4 mile away. If there is any play left on the focus ring, this is the culprit. All camera's are adjusted at infinity. Check if the focus screen is in place. These were interchangable. Is the film back on securely? Did you place the film insert in correctly, should be a click of the two locks. The Mamiya tech is correct and send all components. Steven.