Washing machine drum shudder

I have an issue with my Hoover H-Wash 500 washing machine. It is showing an E08 error, which indicates an issue with the drum/motor.

I replaced the motor with a new one, but the issue still remains. However, I have noticed that when it is unplugged from the motor connector/coupler (pictured), the motor arm spins smoothly. It's only when I plug in the connector that the motor arm shudders. It does this even without being connected to electricity.

Does this indicate an issue with the connector - or could it be something else?