So just had a meeting with Gérard who seems very knowledgeable via my translator, site owner. And we now need to transport it to his workshop in the village for him to carry out a clutch calibration and reset.
His feelings are that the clutch is not engaging correctly with the drive motors. He assures me that whatever the problem he'll sort it.
Hope so.
That recalibration is called "apprentissage" in French, I think. Good luck - I hope it is successful and your problem is fixed.