ZF say who designed and manufactured the gearbox say otherwise….. but what would they know
New seals, gaskets and oil made a decent difference to mine and then after that I XHP’d it which improved it even further.
I assumed you were the original poster which you aren’t and my original response was aimed at the OP. I only have experience of this gearbox in BMW’s so not sure what your issues are. May discuss it with ZF or your car manufacturer and see what they suggest.
Best of luck with it all.