I ~think~ the flywheels were lightened mid way through the 2018 production run in order to quicken the engine response, could be worth trying to find out via importer or factory and see what was different?
Fuel tank breather / one way valve blocked / partially blocked and causing a vaccum?
Or maybe an issue with the fuel pump / breathers if the bike has the tank at the rear? cant remember which year it changed.
these work a treat, made for the job
If you've got brake pressure but no bite get the brakes really hot by riding them them dragging then quench rapidly with water -- repeat 2 to 3 times if nessessary.
Will sort it - doing it for years - no warped disks or anything else.
Loads do it.