Hi,
I have the same issue. It happens from time to time, when the Quad Cortex is on for a few hours, as someone else described here: Tuner/Tap Tempo switch unresponsive during live performance.. Happened once at the studio and now again at a live gig. Changing the preset resolved the issue today, last time I don’t remember, but I had to fiddle with it. Could be a hardware issue? Did someone resolved this?
Best,
Paweł