B7610 3 point losing pressure

[bmwrdr]

My Kubota 7610 doesn't have very many hours on it (~200), and I'm having a problem with the 3 point lift losing pressure. It can lift the rotary mower and other implement w/o a problem, but they slowly start dropping. Even w/o anything attached to the 3 point within a day or 2, it will have dropped all the way down sitting in the shop by itself.
Any suggestions?
Should I invest in a parts or service manual to get into the oil pressure piston?
thanks