We have had problems with the cylinders failing on the inside. Check for magnitizim at the swing control coils and check for pressure at the cylinder hose connections. check for blockages in the cylinder orifices. If all that is good suspect a cylinder failure.
Had the same problem on a 9500...I know it's a totally diff machine, but there are some electrical connectors on top of the 90^ bend where the auger turns and goes out. Apparently the dealer or someone had switched or plugged something in backwards, so it would only swing out about 5' and then not go back in. I switched connectors and it worked perfectly. Again, I know it's a diff machine, but it may be worth a look.
first off, is it electrical, hydraulic, or mechanical. is it trying to swing and can't (has been a problem with the HUR auger). are the solenoids clicking on the valve stack, do all other functions work properly?