Textbook stuff - registration sequence set up, pedal two moves forwards through the sequence, pedal three moves backwards (both are identical momentary action pedals).

However, something is amiss!

If we start midway through the sequence (so the red box is around one of the entries at the top right of the screen) and press pedal three, the red box moves one to the left and stays there - exactly as I would expect.

If we press pedal two, the red box moves one to the right , again exactly as I would expect. It doesn't stay there though! About two seconds later, the red box disappears altogether. Then the next pedal press starts the sequence again.

The book says something about a long pedal press returning to the start of the sequence. This led me to check that both pedals were indeed identical and momentary contacts, not latching - all is well with the pedals. I have also swapped the two pedals around and the problem is always with the pedal that is in socket two - in other words, it is definitely the Tyros and not the pedal itself.

Any ideas what is happening?