Wow/flutter issues P3-24 — measure motor accuracy?

I've had this issue with the table as long as I've owned it. I've replaced belts, re-lubed the bearing and have had no success. I'm wondering if it's the motor.

Is there a way to check that the motor is spinning at a consistent speed? Like, I'm just going out on a limb, take off the belt and use a multimeter to measure ______ to see if it's consistent?

Don't worry, there are lots of very, very expensive Turntables out there which can't hold the correct speed. When you want to check it (also in future for your next one), the best tool is the Timeline Strobe from Sutherland.