Odd Corrugation Change

I have no direct experience on corrugating machines but some on honeycomb production for internal doors.

Worth checking is the alignment of the corrugation rollers. A line drawn between the axis of these rollers should be perpendicular to the in-feed web. Tool low a tension on the in-feed side would cause the web to sag and create the symptom and the direction of curve you describe. You are looking for a misalignment of less than ¼". In the past I have added another pair nip rollers just in front of the corrugators.