With the bravos and Cabrio direct drive washers, the rotor will resist turning very fast or far by hand. It's an internal function of the motor speed control. If you turn the basket slowly, it shouldn't have much resistance and should turn smoothly and silently.
The tub seal is prone to failure. When it fails, the wash water cleans the grease out of the bearings. This leads to the classic grinding brakes or jet taking off sounds.
Your f51 code comes from the basket rpm sensor either being disconnected, dead, or detecting abnormal rpm. Sometimes they come unplugged.