Thanks, Snacko. That's one of the first things I checked, but everything looked fine. It's kind of a random thing though, so I might have missed it. When I look at the RoF controls screen, I sometimes see things jumping all over the place; then it settles down, only to start up again at unpredictable times.
I have another Bodnar board and a spare Hall sensor, so might try swapping in those components and see what happens.
P