The dealer says they have checked the transmission fluid levels.
They also claim there are no adjustments for the transmission shift pattern, and provided no error codes come up, there is no need to take action - have we come to point where we rely on electronics to tell us if something mechanical is not right? What is monitoring the health of the electronics? (Years ago I had a Jag XJ8 whose electronic transmission controller embedded in the gearbox had to be replaced as this was eventually found to be faulty, but only after me insisting there was a problem - no error codes came up in this instance!)
Nissan said the transmission has the latest flash updates. However, they did reset the throttle body control but believed this would make no difference - they were correct.
Thanks all for taking the time to reply...