Proxy sensor switch in the center of the two rollers has no influence on the machine operation.
The micro switch mounted on an angle is what starts / stops the machine.
This has been replaced twice and seems to last when placed on the angle seen in the photo.
Ulimately this set-up should be discarded and replaced with the system below.
This has proved to be the most reliable and maintenance free option fitted to other machines.
Here is the complete option.