Your reports are often a bit emotional 
. It would be nice if you take a few deep breathes before posting, this would make things easier for everyone. I often find that emotions don’t work well in text form - that’s why they invented smileys 
.
Usually issues can be reproduced with a few easy steps and with a route that only has a few waypoints. If too many things are happening it’s hard too reproduce and understand. If an issue only occurs after many complicated and non-reproducible steps happened, then it’s almost impossible to fix.
If you look at this in the simulation it seems to work correct. So it’s impossible to guess why it didn’t work for you.
What I think could have happened, if you missed the left turn to WP5, the navigation continues towards WP17.
After that, to be honest, I don’t understand what is happening.
Where do all these waypoints come from? They are not in the initially planned route. Kurviger won’t add random waypoints.
If you want your navigation to match your planned route, I would recommend to disable automatic rerouting and only do rerouting with consideration and care. No navigation system I have ever seen will perform the rerouting the way I want it to be, so I do this manually, using the rerouting button in Kurviger or by changing the route with a new waypoint.
I probably guide about 30 rides per year. So I know the issue, especially if you need to stop with a couple of bikes in the sun at 30°+ and need to turn around on a busy main road. Therefore, I think I know what I am talking about. Doing any quick fixes on the road, especially if you don’t have the time to double check the results, has never improved a route. What I often do when I take a wrong turn is to look at the map and see if there is for example a possible alternative route back to the route and then I follow that route on the map, without actual rerouting, this usually works a lot better than trying to fix the route.