Brian-
I've confirmed that I am receiving false rotor lock occurrences, but unfortunately dithering by 1% around this duty cycle (at a 1s interval) does not solve the problem, nor does 2%, and at 2%, the motor pitch change is too irritating to be a solution anyway. I'm measuring frequency with the host MCU, and at this duty cycle, with dithering, I'm measuring an RPM of 7065-7290. Or 471 - 486Hz. Does this information shed any light on what the problem may be?
-Chris