Attached is a picture of the filtered Phase 1 PWM signal (green) and its resulting Phase 1 motor current (yellow) in open loop control mode.
Expanded view shows the current variation (yellow) which results in the shutter/jerking. It smooth before and after this section. The higher current peaks are about 400 amps. Not sure what is causing this.
No Load Neutral Test below shows a similar current variation at lower speed. This might confirm the current variation seen above is due to slip and loss of sync as suspected.