I was making a standard scenario called BMc Paddington Dock. It involved taking a loco and train from Old Oak Common to Paddington. I created a bit of AI to make it look interesting. There is a problem with the third signal bridge out of Paddington. I would have a green approaching, only for it to turn red just before I reached it. I tried re-routing the player train, but alas, the problem remained. In the end, I got quite annoyed and changed it to a free roam scenario, and it is almost just as good.