I did not take the spreader off to verify if was form the combine and not the cornhead. I'm running the cornhead as slow as I can because of shelling the corn on the stripper bars. The husk on the ears are very loose and it is easy to shell.
sounds to me like you have done everything possible in exploring adjustments. I experience the same thing with my 42. I don't like it but have not found a way to make it perfect, yet. There are so many variables that effect rotor loss. I just get it set as good as I can and go. Wish I could be better help. Run them all my life still don't know answer.