Thanks premend01.
I took it all apart, and the selector switch was a sealed unit on the pcb, but the hole was very dirty. I carefully cleaned it, and put it all back together, but when I checked it, there was no change.
However, when I turned the dial a few times, all of the programs were now available, although the light flickers on a couple of them.
So I think it is a dodgy connection in the selector switch, so will have to invest in a new pcb if it goes again.