No rear vibration ....until after 1st service.
Servicing procedures do not include messing with either tire - except checking for proper inflation.
Nor would a first service involve opening the CVT.
Retorqeing major assemblies, such as rear wheel, brakes and shocks are supposed to be performed.
Something overtightened?....like a wheel bearing....tire overinflated?
Scooter dropped off lift?
A puzzle....started a rear vibration after undergoing first service.

Stig