Okay, I agree about friction of the piston moving the fluid around but you obviously have much more of that than I. I don't think I would notice it when ram was taken off the quadrant. I have tried the difference during maintenance
and did feel it.. I think, but only by comparing it within minutes. If you give the wheel
a spin, will it keep turning when you let go or stop?
I think I have 3/8" ID lines so friction might be more if yours are smaller diameter? I can't tell you.
There might be something wrong with the unit, like bent piston/shaft, degraded fluid etc. I would suggest you drain the unit and try it empty with the lines open. Put new fluid in etc.