I have the air coming from a pancake compressor (regulated at 85 psi) to a regulator on the machine set to 40 psi. It is a relieving regulator, but I suspect it isn't relieving very well. By completely disconnecting the air line from the pedestal, I seem to have made the issues go away.

Looking at the pedestal drawing in a pdf of the maintenance manual, it looks like there is supposed to be a vent/breather at the top of the air cylinder. The only port there on mine is connected to the lubrication system. It's possible that the previous owner hooked the lube system up to the vent port and tee'd in a vent/breather at the inlet port. Has anyone heard of this being done?