From what I remember of the B707-436 circa late seventies (which had a parallel yaw damper installed) the rudders were effectively `locked` with the yaw damper engaged. Mild dutch roll on approach was a well known feature of that marque and usually countered with short jabs of aileron. Base training on the aircraft included dutch roll exercises at altitude with the yaw damper off - and it was spectacularily divergent!
For those younger posters who may not have had the rather `dudious` pleasures of coping with those somewhat deficient early aircraft please refrain from trying `to shoot the messenger` when the `oldies` reminisce!