Have you had any luck getting it fixed? I'm having the same issue with the same leftmost parameter knob ENC1 in diagnostics. Pushing the button works ECC1 though. Looks like the rotary knob itself works according to the what I'm reading with a voltmeter on the 3 pin contacts on the PCB, so it might be a connection issue elsewhere.
EDIT: I pulled the knob off and sprayed some Deox-It contact cleaner and now it's working!