I would like to give my comments but in TS12, your loco gives one warning and three errors.
Error: Dependency <kuid:546838:1066> is unknown.
Error: Dependency <kuid:546838:1026> is unknown.
Error: Dependency <kuid:487336:1262> is unknown.
Warning: Required container 'thumbnails' is missing.
The warning is about a missing thumbnail container. Not fatal but a sign that the creator did not complete the work. Older content didn't have thumbnails so it can be expected that they are missing but newly created content really should have them.
The three errors are missing dependencies.
enginesound<kuid:546838:1066>
hornsound <kuid:546838:1026>
bogey <kuid:487336:1262>
None of them are on the DLS. Nothing wrong with using non-DLS content but tell people that you have done this. You should also tell people where they can get them from and if they are free. Then they can decide if it is worth downloading before they get to the point were they get these errors.
I would advise you to register your Trainz or don't expect too much help