I had a problem with mine, that turned out to be a pretty easy fix.
One day it was building pressure and right at 100 psi it started making a mad
squeeking and knocking sound, anyway after shutting it off and checking it
I come to find out that the pully on the motor shaft was slightly loose. So
after tighting down the securing allen type screws it was back to normal.
These compressors are pretty good. The things to watch are,
There is enough Oil in the pump.
Now loose bolts etc.
Hope you find a fix for it.