Steam Scenario Failure In The Middle Of Timetable Mode On Tees Valley Line

I am trying to use Tees Valley line but after a certain amount of time I just get a random message just saying scenario failure that just ends the game, this happened while stationary at Saltburn and shortly after departing Middlesborough towards Darlington with no signals nearby and no other problems beforehand (previous signal was clear). Why is it randomly doing this on this route?