Brian Gaff wrote:

You say it's LED, normally they are LCD...

And so is this. A slip of the fingers and the brain.

Thanks to you and everyone else for the further thoughts. My first attempt
at a fix wasn't entirely successful: one of the displaced feet didn't stick
securely and came loose again as soon as I put any weight on it. I'll have
another go.

The feet/sensors strike me as a pretty weak part of the design. Their
springing is just four rather flimsy plastic sprues which connect the actual
foot to the securing flange.