Vibrations under hard regen

Hi All, 

I have a Maker X HI 100 (VESC 6 based), running at 48V connected to a 1KW 26 inch hub motor, with hall effect sensors.

I have run a FOC detection and all looks good.

At regen levels greater than 50A, I get a strange vibration, almost as if the hub motor is desyncing.

I get a similar vibration under acceleration above 70A, but I would imagine this is due to core saturation as I am greatly exceeding the power rating of the motor. 

Any suggestions? Thanks!