Need Some Assistance With Rega related Issue

A while back I upgraded the Rega motor on my TT. It is a standard Rega uprgade kit.

All was good for a couple of years - i.e. until recently when I tried to play 45rpm albums

The result was terrible - it never reached 45 RPM and experienced huge speed variations

I thought it might be the belt - so I ordered a couple of new ones which arrived yesterday

Although it was better after installing the new belt - it was still bad

I stripped down the TT - cleaned the Subplatter spindle, bearing, brass bearing housing and topped up with fresh oil.

No joy - still sounds bad

I had no problems with the old motor  at 45 rpm  - should have kept it - damn!

Since the speed is adjusted by the pulley - I think it rules out issues with the motor electronics? - because there is no issues at 33rpm - rock solid.

The only difference in load to the motor is an acrylic platter which is a little lighter than the glass platter it replaced.

Any suggestions would be greatly appreciated

Thanks Steve