I ran a scenario last night from Leeds to Manchester with a class 47. Loads of AI coming the other way. It went very well. I thought I'd try it again using the class 45. Didn't alter anything else, just the locomotive. When I started the scenario I was spawned on foot at Ashton under Lyne. Tried again and this time it was Batley, then Dewsbury. Changing the locomotive back to a class 47 did the trick and the scenario ran as expected. This is a new scenario, created after the recent update so no idea what caused it.