Mapquest direction layers: Route line is interrupted

Hello again,

since a few days we have problems with our mapquest javascript code. We calculate a route and use the DirectionsLayer.extend to create markers on the map:

Our javascript: pastebin.com/jUZPHnSU

But if you execute the javascript you will see that the route line is interrupted:
Screenshot: ibb.co/0tmMKnR
 

If you try to drag the route, then it shows shortly correct, but after a few seconds the map shows alternative routes and seems to be broken:
Screenshot: ibb.co/9rwX8gt

Whats wrong with the direction layer?

It works many years until now.