When I get to Hempstead and its time to walk to the other cab for the return journey, I cannot get the game to recognise Ive started it correctly. I've done it five times including without saving. Its defianately a glitch or a bug. I can start the train but the game doesn't recognise I've started it correctly so cant finish the scenario. I cant even get to the charge the brakes notification.
Ignoring that you've posted this is completely the wrong section, I did that scenario very recently on PS5 and had no issues. Have you definitely shut down everything in the first cab? Lights off, brakes to Emergency, key out?