Something quite strange happened to me during my last mixing session on one of my SC6000Ms.
Just after doing a manual backspin, the motorized platter started to vibrate. this happened twice during this session.
The platter continued to rotate normally but vibrated strongly until I stopped it.
Then everything returned to normal.
Has anyone experienced anything similar on motorized equipment?
This does not happen during scratches, only after doing a backspin.
Not in one of my four decks.
IIRC, the motor is independent of the spindle (the encoder).
You’re right, it seems to me that these two elements are independent of each other.
This is what puzzles me even more about this phenomenon.
The vibration seems to come from the motor and spreads throughout the platter. It’s a rapid vibration, a bit like an Xbox controller. It lasts for at least ten seconds.
I’m going to conduct some tests to see if I can reproduce the phenomenon during backspin and try to make a video. The sound of the vibration is clearly audible; it’s also reminiscent of the noise when an Xbox controller vibrates.
This has no impact on the player’s experience since once the track stops, the motor stops and the vibration disappears.
But I fear these are the first signs of an underlying problem that could lead to potential engine failure or at least premature wear.
Perhaps it’s a problem with aging grease; I’ll run some tests to see if I notice any drift.
I too worry about the wear on your motor. 
I wonder if it’s not the backspin itself, but rather the force of the backspin and if you could easily replicate by holding the disc down (stopping rotation of the disc only) and progressively adding force, making the motor work harder and harder until the aluminum platter stops.
This, of course can be done in a less destructive way by touching the side part of the platter to see if that induces the vibrations.
It’s hard to think that the oil / lubricant is the issue given that it takes an action, such as backspinning, to induce the fault.
I wonder if it’s the code and/or circuitry that manages the PWM (if that’s what it is) that could be the problem? I say this because I’ve had some custom drones that would make chimes upon startup of the device, and those chimes came from the PWM controllers managing the motors.
All of the above is me “thinking out loud” 
Well, I ran some drift tests in dual-layer mode with an instant double, and no drift was observed. The tracks remain firmly in sync, with no fluctuation or even the slightest phasing effect. This rules out any grease issues for me.
I removed the platter and played a track out of curiosity. You can clearly hear a vibration during playback with the platter removed; you can even feel it by touching the rotating mechanical part in the center.
So I wanted to check on my second player if the vibration was also present with the platter removed. And it is also present, with the same level of intensity. So I think it’s normal. Check on yours if you’re curious to confirm.
However, once you put the platter back in place, you no longer feel any vibration during playback. It’s as smooth as butter.
I tried to intentionally recreate this vibration phenomenon afterward during backspin, but without any success; it never happened again. Perhaps removing and then replacing the platter solved the problem. I note that it was quite difficult to remove; it seemed stuck, and I had to apply slight force to get it out.
For now, everything is working properly, but I’ll keep an eye on it.