I had similar issue with CMT router. They are all the same, made of the same parts, just whether you want a orange, yellow or black one.
My router was circa 10 yrs old and failed onto slow speed. Solution was to change speed controller board. Cost £80 incl vat and pp but way cheaper than a new one and mine had only had light use from new in a woodrat so mechanicals are all pretty much as new so worth doing. TBH, if it has failed to full speed I'd of just lived with it as I don't use big dia cutters anyway so run everything on full.
Simple to change, 2 more screws and the black squareish donut is the speed controller and just lifts off and is just a case of moving spade connectors onto replacement and reinstalling.
S