i had that same noise,somewhat last year when doing green stem beans  with our 9500 and a 930 flex the later in the day thhe noise became less..  the deere mechanic walked beside combine and said it was the vari speed cylinder drive belt slipping,put new belt on, and still some but alot less .spent an hour re aligning the sheves and noise went away, like you the noise wasnt there when we were doing corn

smoke