I was helping someone to make a train network mostly identical to the one in this video - https://www.youtube.com/watch?v=G9GWl4X2ln0&t=330s I did the exact same thing on a different world during my ongoing SE playthrough, and it worked just fine.

But in this world, using the same settings for a train caused them to initially work, but after a trip or two, the trains would unassign themselves from the train group and remove all of the interrupts, thus only leaving the loading station in the schedule, going there and staying there indefinitely. We first suspected the Exotic Industries mod, but eventually finding removing just this mod from the modpack fixed the issue.