3-Point Hitch 3-Point Hitch Lowering Itself While Working

[Norcal M5]

While carrying a large sprayer yesterday, I noticed that when going downhill on bumpy terrain the 3-pt was lowering itself. Not good, as my sprayer would start dragging on the ground. I think the problem is the raising and lowering lever, which would move due to the orientation of the tractor when going downhill, plus the shaking due to the roughness of the row I was spraying.

Is there some adjustment to make the lever harder to move?

 

[Dr_Zinj]

Don't know on the New Holland; but my Bobcat CT230 has a twist knob next to the floor just to the right of the 4 wheel lock pedal. Turn it one way and the 3pt sinks down (and moves faster) turn it the other way, and it stays pretty much in place and moves slow.