My daughter is currently traveling with an itinerary of London-Italy-Croatia-Austria-Brussels-London. Her group tried to get a train today from Trieste, Italy into Croatia, but they were not allowed on without a reservation, even though the app said no reservations were required and the train wasn't full.
They booked a bus journey instead but she is now worried that she will hit the same problem with later trips. Her itinerary includes high speed trains between Villach-Salzburg on Wednesday and Salzburg-Frankfurt and Frankfurt-Brussels next Sunday (she has a reservation for Brussels-London).
Again, the app says no reservations are required but might could this be changed leaving them stranded the last minute again?