I have a faint memory of this being listed in known bugs a long time a go, but I might be wrong. So, if one saves a game when loading passangers at a station with a Talent2, and thereafter loads the game later, once passanger boarding is complete and the doors have been closed the door indicator won't light up and the door brake interlock is not releasing. I believe some parameter of the train is not correctly saved and this breaks the simulation when resuming a save, but is there a workaround for this? I have tried cycling the power/brakes, hand brake, the MCB and the doors on and off, but that does not have effect.
I think "save game" is one of the feature that never worked properly on TSW2 and has never been fixed. I tried using it at the beginning, but I gave up. I think you did nothing wrong.