Why no braking on LRP BL motor

[OneKiwi]

Q time...
I have a 7.5T BL x11 motor that had a problem it made a strange noise and got REAL warm..
It was behaving like a really loose slipper.

I took the cap off and removed the rotor after it had cooled and saw that it was covered in like an apoxy and fine hairs.

I proceeded to clean it up and then reinstalled now it drives fine got good power still but there are next to no drag or brakes.

It is the motor as I tested another with the esc and thats fine.

What could it be?
Is it screwed?
Could I just swap rotors or the other parts?

I haven't tested swaping rotors as I don't want to risk damaging the other one, so I thought Id ask here first

BTW the rotor is black and another motor which is the same has a goldy coloured

Thanks