I will go to milan centrale from Thun on 29-09-2024, but I found out that the train on that day has to change to the bus via Domodossola. However, EC51 on any other day (28-09-2021, 30-09-2024 for example) could arrive at Milan directly. so I would like to know the reason why the train has to transfer on 29-09-2024.