5 months ago I put a tiny bit of ball bearing grease on the A7750 rotor. The annoying noise was immediately gone. Only a nice 'purring' sound when I hold my wrist to my ear.
Just opened the caseback and as far as I can see it hasn't leaked into the other parts (it onlt melts above 110 dgrs Celcius) , neither is the rotor slowed down. Watch keeps perfect time so far.
HOWEVER, when you ask The Zigmeister he'll tell you NOT to do this. So I'll have to see what this means for my watch in the long term......
I also have a gen Oris watch with Valjoux 7750. It does make some hearable noise, but a pleasant one and not even close to the grinding sound as some A7750 have.