Well post #41 in that thread was written by Messick's. The way I understand it, Kubota, in order to solve the jerky, went to a Gl 10 series valve. As far as Messick's knows this solved the problem.
I guess THAT makes sense. To repair the L3800 at my dealership, they did the same. Install a 10 series valve, which according to our TBN member, worked.
Now according to LD1 in post #43 "That valve change was around SN 61000, and only ran until ~ 68000, and then they changed again, and then yet again."
If the 10 series worked, and according to Mesick's and the TBN member, it did, WHY DID THEY STOP USING THAT VALVE?
If I am misunderstanding these posts I apologize, but that's the way I read it.
Hopefully this all works out for you. Test dummy was always a tough job.
Bill