A real shot in the dark here: The SP-H9 has a toe switch, as I understand it (never used it). Is it possible that internal switch on the Mission is ‘stealing’ the right footswitch from your Ampero?
I would try this: TS cable out from the Mission expression pedal. Or better yet, unplugged from the H90 completely. Try to calibrate the Ampero dual switch on its own, using a TRS cable.
Then unplug the Ampero, use the same TRS cable to the Mission, and calibrate the SP-H9 by itself. First as an expression pedal, then re-calibrate it as an Aux Switch, while pressing down on the toe switch.
