We have the same problem with our 7720 titian II. We found out that there is a rubber strip that fits between the back of the sieves and the carrier that the seives sit in. It is an easy fix but very time consuming you have to pull the chopper, seives and the seive carrier out in able to get the bolts that hold in the rubber strip. The best way we found out about this was talking to our deere dealer they pulled a picture and it made it easy to see what the purpose that piece did.