Hi Machineco,
I have experienced something near to what you've described.
During several rehearsals, my setup for the current patch was changing spontaneously without any action !!! (volume, bass, treble,...)
I've shut down my samsung S6, thinking it was a BT interference and it carried on ! It was exactly as if someone was playing with my FH knobs.
No explanation. I hope it will not happen during a gig...