...the movement isn't smooth though
Are you talking about how the probe swings wildly when it's dragged near the starting point of the wire? Or is there another issue?
If it is the issue you could disable the lines of code that rotate the black probe towards the starting point of the wire. So the probe would always stay at it's original angle.
You might also consider moving the multimeter so that you are not trying to probe a point right next to it.
If you don't want to move the multimeter you could stop adjusting the angle of the probe when it's within a certain distance of the multimeter.