Sorry to hear you are having trouble with your lathe Ken.
Can you expand on the description of what it’s doing ?
Does it work normally with no load on it, and slow down when you start cutting ? Or does the speed vary erratically?
Is it still under warranty ?
I tightened up the belt a little more and was able to drill two pill holder blanks with a 9/16 bit with no problems. Speed did not vary while drilling. I did blow air through the vent holes on the control box also. Hopefully all is well.