Hi , i had have the same problem , the motor was defect.
you can test it by connecting another motor on the same wires.
if the good motor has the same problem then the stepperdriver had to be controlled.
My printer had also an defect pcb , that one where the wires conected at the side.
check that also, .
I got an new motor and pcb from them , but be patient , there reaction is always slow and , can not be .
make an video where you proof the hole thing , then they send everything to you .
i had to wait 2 months , hope you get it faster ,