Hire game testers! So many broken scenarios. Latest one I've found is: 5d50 thornaby depot - darlington Literally no way to actually start that journey. You cannot turn right at the junction you need to!
I've done it many times so you know it works. It was impossible to do from the map as I think there are two points very close together. You've just got to make sure you switch the right one. Change one, check the map and correct if necessary.
I'll try it again today, it's always been tricky but it's always worked in the end. Maybe it's a new issue. Sorry you haven't been able to complete it. The 0645 or 0650 leaves from a different siding and doesn't need that point changing if you fancy trying that, it's an identical run otherwise.