E-motor jerking back and fourth

Hi. My extruder isn’t extruding. The motor just jerks back and forth. It seems to be skipping steps.

I can move the big cog and extrude very easily by hand so there’s no mechanical issue.

I’ve tried trimming the voltages on the motor driver to everywhere between 0.2-0.8, but it makes no difference.

So i’m guessing i need either a new motor or a new driver?

How do i know which one?

Did you swap the driver with either X or Y-driver, to check if it is a driver or motor issue?