I have an 806 that I purchased last year and am finally attaching a heavy implement on the 3pt hitch. when I raise the implement it maintains its position but does this correction every few seconds you can hear and feel. This happens both with a cold system as well as when it is fully warmed up and hyd fliud is full, clean and filter has been replaced and screen cleaned. Draft control is in the off position, no external/auxiliary hydraulics connected. Is there a particular valve I should be looking at for this issue or other? Thank you