Could you make the route public so that I can look at it? (Go to “My” then “Journeys” then click the sunglasses next to the route.)

Tony, I have saved your route and opened it in my (Android) app. It looks the same to me - both showing 1620km. 

 About the only thing I can think of is, if for some reason, the app is using an older copy of the route? You haven't said which version of the app you are using but on my android version, on the page where I choose routes to load there is a 3/4 circle that refreshes the files. You could try that.

Alternatively, on the Website I'd try saving a copy of the route under a different name and then open that (new) one on the app.