I tried to create a formation with Bnrdzf 463.0 Diesel + BR 218 but when selecting it, no other wagon options (like Bnr451 or Bnr451.4 for example) are available, not even locos (like BR 218 for example)
German content is not important, they don't take the time to fix bugs. An example of this are the Dostos from MSB and RSN or the Talent from SKA. Errors were reported over 1000 days ago and have still not been rectified. https://forums.dovetailgames.com/threads/light-bug-on-dostos-roof.27082/#post-768754
And another patch without fixing the bug with the Bnrdzf 463.0 Diesel in the Formation Manager. Unfortunately, it is still not possible to create a train formation for the Cab Car. The bug has been there for almost a year now and once again it doesn't matter. It can't be that difficult to fix this error.
As said a few times on the forums, i tried to fix that problem. I spent a lot of time to get the idea why it's not working. Unfortunately i did not found the cause of it. Setup wise it is all fine. It should work, but doesn't. No one can tell me why. So i can't do much more yet. Besides that, the only usable loco for that cab car is the BR218. There are plenty of predefined consists already for that train. Use them. If you want to have such a cab car at the end of whatever train, use the electric version. That is working as i know. Looks the same from outside.
