Service 6V60 ardingly aggregates to Acton tc part 2. I completed part 1 ending at Haywards Heath started part 2 the instruction is to decouple 12 coal wagons did that and the game won’t recognise I’ve done it.
It may take an unreasonably long moment for the game to realise that you have actually uncoupled. Could this be the issue, or did you wait for a good 10 seconds or more after uncoupling?