@dc42 Yep, the period is definitely two cycles per revolution. It's also consistent on all motors and encoders I have, including 0.9 degree steppers and CUI AMT10E2 capacitive encoders.
Here's just one revolution out and back. I marked the shaft and watched as it went. At this scale (and with the other issue resolved), it's more of a sine cosine wave than a sawtooth pattern. Between that and the two cycles per revolution period, makes me think it has something to do with pi, but I couldn't guess what.
fixed-ol-r1-s200.png