A bit of an update
Well, so far I have changed the wheel to a different bike, with the same result.
I am now awaiting a new controller from the dealer, and if that doesn't work, then the wheel itself
will be changed.
The theory is that the controller does not always know what position the motor is in, so it is
"Hunting" trying to find the position, thus the vibration.
However it turns out, I will post on the board.
Thanks for the replies to date to everyone!!