Wahoo KIKR core service

Anyone serviced their own KIKR?

Mine suddenly sounds bloody awful. I've taken the cassette and freehub off and changed and headed the axle, but it an looked fine anyway. Took the plastic cover off and exposed the belt, bit that all looks clean and solid. 

Can I do anything with the "spinny magnet bit"? Is it easy/specialist tools etc!?

Can anyone recommend a particular guide to follow?

Unfortunately, the shop I bought it from went under and I've had it over 4yrs now I think so well out of warranty now anyway. 

Annoying time for it to be out of action!