Your Cabrio was manufactured in 29th week of 2006.

F51 is failure of the RPS (rotor position sensor) which is on the motor stator.

The basket should rotate freely with the rotor removed. There may be some magnetic cogging with the rotor in place but it should still otherwise rotate freely. Could be a bad bearing on the drive shaft if there's notable resistance or drag to rotation.

The basket floats slightly upward (via air captured in a dome under it) to physically disengage from the drive cog when the machine fills with water so the agitator can oscillate separately. It settles back down for spin when the water is drained. Lint/debris, mineral residue, or even rusting on the drive shaft can prevent the basket from slipping properly up/down. Grabbing the basket and lifting on it should indicate if it moves up/down OK.

Not unusual that the tub suspension rods wear over time and contribute to increased off-balance. A flaky RPS can also cause excessive off-balance alarms (if the load isn't really off-balance). There's no physical off-balance sensor switch. Off-balance is sensed by the motor controller software via monitoring the rotational characteristics and inertia as read through the RPS.

Thanks. Basket would still not turn until I forced it back and forth. It 'broke free' of whatever was holding it and turns freely now. I want to break it down further, removed agitator, but the basket will not come out. Thinking of applying upward pressure on the basket while tapping the shaft. I'm guessing a bad bearing and corrosion are keeping the two inseparable. Perhaps it is a new marriage and they just want to hold each other. Your thoughts?