We've been working through the Williams startup sequence from pinrepair - got to looking at the bonus unit and now more puzzled... see photo.
The bonus unit doesn't move at all during the startup sequence (which it is meant to do) .

1. It looks like there should be two solenoids on the unit, but as shown in the photo there's only one and no sign there ever has been two - is this right?
2. Assume the bonus unit senses zero position via the "snowshoe" type wiper unit (so no blade-type zero position switch)?