I had a similar problem on my 9500 - The feeder house developed a fast creep, but reel lift was fine, so hopefully your problems aren't related. I'm assuming the 9650 valve block is similar.
No external leaks, and the problem was still there with the accumulator isolated, so I guessed the problem was in the valve block. Like you, replacing the 'lower' solenoid's orifice, o-rings and pin made zero difference.
On the opposite side of the block is a plug with a hex key hole in it. Lower the feederhouse to relieve hyd pressure, isolate the accumulator and remove this plug. Inside is a spring and a poppet. In my case, the spring had broken, and installing a new one got rid of most of (but not all of) the creep. I'm guessing that this is some sort of relief valve setup, because without the spring in there, you can't even lift the feederhouse because all the oil bypasses.
A good way to test is to raise the feeerhouse all the way up, hold the button down and watch the accumulator pressure guage on the LHS cab pillar until it stops rising. Then watch to see if the pressure drops.
I guess the reel lift would have a similar one-way hydraulic setup, so that may have the same problem, and would be worth checking before you pull the entire hyd. block apart
Hope this is some (belated) help.
