I was trying to do some EAA on the moon over the weekend with my Mach1, and I found that anytime I clicked the Lunar Tracking button in the ASCOM driver, it would reset back to Sidereal after a few seconds. 

Custom rate did work correctly.

My procedure this night:
1. Polar align via Sharpcap
2. Use SGP to solve and sync
3. GoTo RA/Dec of moon in APCC
4. APJog to nudge moon into center of frame
5. Press Lunar Tracking button in ASCOM driver

After a couple of seconds, the ASCOM driver would set back to Sidereal with no errors reported.