I have a strange issue… While accelerating both motors seems to pull similar amps according to metr. But once the top speed is reached, one motor goes to negative amps, as if it is breaking and I can feel that the board behave as a single motor drive.
Maybe try connect the functional motor with the wires that connected the slagger,
and see If the same happens now to the functional motor, then you’d know if it’s esc.
It’s the piece of shit flipsky fsesc. They are known to drop out a single side. Many people including myself have had to send them back to China for repair. Find a more reputable vesc.