Example: Departure, May street (Hammersmith and Fulham). Destination, Fenelon Place (RBKC).
The route says Turn Right onto West Cromwell Road. This Junction (North end Road and West Cromwell Road) has be a No Right Turn , from North End Road for Years.
How can this routing error be fixed?
It is the same for any Start/ Destination that involves a Right Turn from North End Road onto West Cromwell Road.
OSM shows no restriction when turning from North End Road onto West Cromwell Road so navigator will give the turn right instruction. Based on your comment that this restriction has been in place "for years" I've added the no right turn to OSM. The correction may take up to 2 months to show in Navigator.