Prerequisite: The next available journey is for an ICE. For me, it's the first ICE route in Chapter 4, "ICE 11 Frankfurt (Main) Hbf". Steps: 1) Go to Timetable mode 2) Pick BR442 Talent 2 3) Select any service - obviously the last 3 services ending in the depot are quickest if you just want to reproduce the issue. 4) Complete the service 5) Pick "Continue Journey" from the end screen menu 6) Marvel at the wonder that is the 1 car BR442 Talent2. I hope the passengers sitting at the back brought an umbrella! I have reproduced this a number of times with this combination of timetable service and journey, but haven't tried other combinations of trains / routes to see if it's something specific to Köln and the Talent2, or if it's a general bug where the timetable service sets a global "you must use this train" variable that confuses the journey setup. Side note: I couldn't actually start the journey with this 1 car Talent2 - I could start it up and unlock the doors, but the "Loading Passengers" trigger didn't fire, and the signal was stuck on red. So the best I could do was just slowly crawl between the two signal points. But in the grand scheme of things, "The journey scripting didn't cope with the wrong train spawning" is a lesser bug than "the wrong train got spawned"...
Just had the opportunity to test the same issue, switching from an ICE timetable service to the RE9 journey service, and...