MainStage - Sustain reassigning itself

During a show my sustain pedal seemingly reassigns itself at random from 64 to 7. It turns the volume down to 0 until I press sustain then it jumps to 127 and I can control volume with the expression pedal ( but obviously lose use of sustain).

When I try to reassign it back to sustain in the settings it refuses to do so and will only work again with a full laptop restart. I have tried just restarting MainStage but it does not work.

The sustain pedal is connecting to a midi splitter directly into the laptop alongside the expression and patch pedals.

It has done this three times in the previous show and I am at a loss as to how to fix this. This has never happened before. Any ideas? The show was previously working fine for weeks.