I took a quick look at this issue, and I don't believe there is a problem with APCC. APCC is properly adding the rate supplied to it whether or not pointing and/or tracking rate correction is enabled.
However, the ASCOM driver is sending an RA movement relative to zero, which is maybe the problem. The ASCOM definition for this method is unclear if the rate should be relative to sidereal or not. It only states that the previous tracking rate should be restored when the move axis rate is set back to zero.So it may be the structure of the command sent from NINA? It's supposed to specify a slew rate? (Where "supposed to" is apparently clouded in lack of a clear standard, but in this case if it did, it would work?) How does it know the proper slew rate?
Maybe I should just vanish from this discussion and let Dale or one of the NINA folks decide if there's anything to do. I'll just make a mental note not to use the arrows in NINA.
Thank you for taking a look and the explanation.