Spacedeck Owners: Have you experienced this?

Hi everyone:

I noticed that there was some oil on the plinth today, and since it's been about 6 months since I've done anything maintanence-wise with the table, I thought I'd refill it...When I put the deck back together, I noticed that the rubber belt wildly vibrates when the platter is spinning. (I've toyed around with motor placement, readjusting the belt a few times, etc.) I've never noticed this before. Have you seen this? If it isn't normal, how do you fix it?

Thanks!
Aaron