I would take this as a sign that a new sub crawl was in order. Start over with the new sub driver, as if you never had a sub. Turn all the modes off, re-integrate the sub via it's best position (which may or may not be where it was), then re-run Audyssey (or whatever app you use).
It's a VIRTUAL channel unless stated otherwise.
Last edited by RayGuy; 08-07-2019 at 10:49 PM.