Hi, and thanks in advance for your help.

The primary symptom appears to be the bottom spray arm doesn't rotate, and hence the lower rack doesn't get cleaned properly. The blue circle sprayer spins, but the grey arm it sits on does not rotate.

I've removed the arm, and checked there's no blockage. There isn't. Water flows strongly out all of the holes when it's under the tap.

The pump sounds like it's working fine, and if I open the door during a cycle there's water all over the washer.

Any obvious things to test?