Our 920 platform on a 9400 bounces like crazy when dial-a-matic in 2nd or 3rd cutting pressure position. Header works fine in 1st position but must be adjusted with more down pressure than I like. Have adjusted box on end of head several times as per book. We also have adjusted header drop and dial-a-matic flow screws located on valve stacks and adjusted nitrogen bottle at one and two turns out. Anyone with some ideas for a solution?