Now the entire rear hydraulics degrades when connecting a PTO with the tractor. Many thanks at this point to Marhu who helped me here!
At New Holland T 9560 and Case IH Quadtrac 620, the rear hydraulics no longer breaks down, no matter what is specified. These tractors does not bother her.
Now the hydraulic Sound is recharged by this script, if is missing in the Fzg.xml. (Even in the standard New Holland T 8435 lack of ..) Then a small clue is written to the log.
Script und Idee: Ifko[nator]