Changing Destination of train multiple times along route

I have been experimenting with having different destination on trains depending on what the destination of the train is. I have got the destination to be set at start of the route and this works fine. But for some services The train starts in a Depot I wanted the destination to start by saying "Not in Service" and then after arriving in station where the service starts from it changes. I have got the destination to change correctly but when I view the route in the route viewer I always get this error:

Critical The route and train loader encountered the following critical error: Cannot perform runtime binding on a null reference

and I was wondering how I could fix this error. I haven't had any other issues with route so if I can't fix the error can someone tell what it means.