although I have an SDS, I don't know the characteristics of the competition. It is important to get one that has variable frequency on the current delivered to your turntable. It is the alternating current (AC) frequency that the motor uses for turning at a specific rate. That's why they are called synchronous motors.
But SOME turntable motors use Direct Current, such as Origin Live turntables, different from most turntable motors.
Just a thought.
PS- DID YOU CONTACT VPI ABOUT THIS? It may be a problem with the belt, or with the pulley, with an inexpensive fix.
PPS- on the very distant possibility of inaccurate current frequency from your Power Company, you might call them to ask about their quality control of the 60 Hz standard. A VERY distant possibility, but perhaps worth checking?