9570 unloading auger slow

granted, its a smaller auger and goes slower than the auger on its bigger brothers, it seems like there are times when it will unload really fast, then all of the sudden, its like one floor auger quits pushing and it unloads about as fast as you can combine. Two or three times later, it will unload fast again. Checked the chain, sprockets, flighting looks fine, nothing blocking the "up auger", etc. Any ideas? I have had it to the dealer once, and they said it was fine, and after combining wheat have it back over there again. It is very sporatic, anyone ever heard of anything like this?