Sorry guys still can't accept this is the cause of the problem. I hear what you are saying but 10mm of flex at the fork tips will translate to less than 1.5mm of fore/aft movement at the bosses. Even taking into account this travels in an arc, the distance between hanger to brakes can only vary by much less than 0.1mm. With all the play in the system surely this cannot significantly increase pad pressure at the rims.
I still maintain incorrectly toed in and set up pads are the primary cause of the problem. They start the judder as they prematurely grip and release (snatch), this gets amplified through play in the cantis and brake bosses, ultimately then violently flexing/juddering the forks.
Many cross bikes cannot be fitted with fork mounted cable hangers as there is no hole at the crown