Eric,
It's all back together and working
The problems I found were:
1. There was a broken shim under the circlip that holds the base together. This allowed the base to lift so that the large gear was sitting on top of the two small motor mounted gears. (hope that makes sense). When the motors turned, as the gears were not meshed, the forks didn't turn. I fitted a new shim but it's still a little loose.
2. The spring that is supposed to hold the degree wheel in place, didn't. As a result, the degree wheel was turning with the forks. This made it appear that the forks weren't moving.
To get the motor gears to mesh properly, I had to release the screws holding the motors and wiggle the motors a bit while the were running. This only took a few seconds to click in. I also had to apply some grease as there was next to none present. Still have to work out the correct fitting for the spring.
The clamp was in the locked position for it to work properly. It's also quiet.