Hi Billy,
where is the faulty bucket, very left or very right, or somewhere in the middle of the console?
If the faulty bucket is very left (or right), remove the i/o modules and check the S9E 10way ribbon cable on the lower bus card. The S9E bridges the TR MPX signals including MPX enable (VCA / TR switching) among the bus card.
If the faulty bucket is somewhere in the middle, as a start, check the supply voltage (+/- 18v, +11) OF THAT BUCKET using the module extender.
Hope this helps,
Domburi