We are flying out later today to Frankfurt and I was initially under the impression, based on information from Seat 61, that ICE trains could not sell out (although I understand seat reservations can). We were planning to buy our tickets to Würzburg when we got there so as to avoid committing to a specific train.
Upon checking the DB app for upcoming trains today (just to see the prices) I noticed that many trains say "Train fully booked" and I cannot seem to book a ticket through the app. Am I missing something? Should I book tomorrow's ticket now while there are still trains available?