If Art Q is correct about the steering cylinder seals being bad again, be sure to check the cylinder itself to make sure the cylinder walls aren't scored and causing the seals to fail.
I had hydraulic cylinder seals replaced under warranty, and they failed again too soon. I tore it down myself and found that the cylinder walls were scored. I replaced the cylinder and the seals and it's been ok since.
Another possibility is worn tie-rod ends, but on a tractor I'm not sure that would give you "lots of play"; more like "a little play" or "no control at all" if they break.
I'm not familiar with your tractor, but if there's a u-joint between your steering wheel and the power steering unit, you might check for excessive play in that joint.
Finally, another possibility, if you're short on hydraulic fluid, you'll have lots of play and kind of erratic jerky steering.
