Generally I've found 'shake' when the knife is running comes from wear in the hinge pivot bushings on the assembly that the wobble box is mounted on . Its cheap to fix but left unaddressed becomes expensive .
Digger, how can you tell if these bushings are wornIJ I've pryed on them with a 3 ft bar and can't feel anything or do you need to take them apart to check themIJ Thanks! CW