Hi Chipenter,
There is no screw type adjustment, but there is a steel washer between the crown wheel, on the teeth side and its support bracket, estimated at 1/2mm thickness, which could be adjusted.
The crown wheel does appear to function correctly, and reicprocates the gear quadrant, I think it is frictional build up in the bearings that is preventing this part from operating.
Another point I forgot to mention, do you know how many turns are required on the string, to provide the necessary torque to enable the meat to reverse.
Cheers David