Crankcase filter oil return pressurized

[buckeyemtnman]

I have air pressure and lots of oil coming from crankcase to (yes, towards/into) crankcase filter.....what would cause this? When I first start the cm871 in the morning, there is no major blowby at bottom of blowby hose that hangs down below oil pan, and no pressure/oil coming from crancase side towards/into crankcase filter housing. But if I release tractor brakes and move forward 10 feet and set my brakes, then I have major oil coming from blowby hose to groud and pressure/oil pushing into crankcase filter housing from the oil drainback tube.....any ideas? Is it my air compressor? I also have oil below my air dryer when it purges.