The ASCOM driver should be thinking of rotator positions in degrees, not rotator steps so it's a bit of a mystery - and I wrote it!
Maybe there's some problem with what is reported, the rotator hardware has to be addressed in terms of steps while ASCOM uses degrees. Perhaps there's some problem with this conversion, especially if the steps go outside the range that is expected to be converted to 0 to 360 degrees.
What this waffling is leading up to is can you collect a driver log for the same period as a SGP log that shows the problem. There should be a Trace On checkbox on the driver setup and the log will be in the My Documents / ASCOM Logs folder.
A driver log would be useful anyway, it will give chapter and verse about the driver state.
I'll look at it but it's going to take a day or two before I will have the spare capacity and a driver log would help to show what's going on from the driver's perspective.
Chris R