I’ve spent a lot of time tuning the PID and have made some progress. However I don’t think I can get it to be more stable in the hold mode because of the backlash. I’ve eyeballed the backlash with a ruler and it’s about one degree. The only motor/gearbox combination I found with less than a degree of backlash is a precision planetary gearbox driven by a stepper motor with a 1/4 degree backlash. They are sold by Stepperonline. I think the only way to get away from the backlash is to go with a stepper motor w/o a gearbox. Stepperonline sells them with encoders. I will probably try that later.
Chuck