45 rpm on VPI Aries

Anyone have a problems keeping the belt on the 45 position on an Aries table? I have the 300rpm motor. After several revolutions the belt slips back to 33 position.
Thanks for the help.
I have a scout. I forget exactly how the Aries works but on my TT the motor is completely separate. If yours is, make sure it is completely level. If not, the belt will slip off. Also, its a good idea to check everything else involved to see if it is bent, off center, worn, different height, ect. It doesn't take much to get the problem you are having.
VPI has wonderful customer service. They will have the exact answer. Checking everything is a good beginning, but the bottom line comes from VPI
..sounds to me like you need a new belt....
Thanks to all.
If your motor is at a height close to the transition from 33 to 45 it could do that?
Try raising the motor? I would also take the recommendations from the above posts.