Create a route in the 'Route info' menu. Select 'Save as' from the options list. Message box comes up asking to enter new routing points set name with 'New set' as default name. Enter name '04-16' and click 'OK'. It is now in the route listing under 'My places'. In 'Route info' menu, add a waypoint and then select 'Save as' from the options list. Give the new file the same name, '04-16' and click 'OK'. Message box appears saying 'name already exists, do you want to save anyway?' Click 'YES'. Message box comes up asking to enter new routing points set name with 'New set' as default name - same message box as when saving the route the first time. Modified file is not been saved in the 'My places' route list.
Same problem here - which has super annoyed me for quite some time.
The workaround I use is to always save under a new name, then delete the old route, and then rename the new one using the old name. Inconvenient, but the only solution I could find.
[What also doesn't help is that the newly named route initially does not appear in the list of routes - I have to go back to map view, and then again to saved routes, to make the name appear in the list. Also super annoying.]