I will bring it together with this 'bombshell'.
I believe I am going to have to remove and repair the motor.
It is grinding away with what I am sure is either rust, or something dropped off and trapped in the magnet gap somewhere.
It is not a 360 degree scraping/zinging, but at the point where the wheel binds up, I can rotate it back and forwards and I can feel it binding.
It does not feel like it will simply wear down flat.
Something is going on in the motor. It might be connected with the fault I was trying to fix before Christmas, the controller cut out and did not allow high phase current at low speeds.
I think the only way is to remove it and open it.
My interest in attempting this work is 'zero'.

First step is to open it up. It seems this is the method? I am scared of very big magnets that can chop fingers off.
https://youtu.be/VeL0FQom1CE?t=156