In the session editor where you place your trains and setup the rules and driver commands, you can adjust the engine specs. This is actually new feature with TRS22 because prior to this you would need to edit the config file manually.
Use CTRL+ right-click on the cab car you want to update.
You should see the engine spec listed. Click on that and scroll the list and choose something else such as something from a diesel.
If you don't see that, you can try edit in legacy mode (I can't remember how it's written) to have access to some hidden settings.
I know the diesel engine spec isn't correct. The problem is the AI don't like to drive backwards unless they have a locomotive and will go through great lengths to not to do that including turning themselves around. By putting in an engine spec, by replacing the default one, this will fake out the AI into thinking this is an engine.