Some assets are wrongly categorised as kind "nd" by Trainz Objectz due to a minor bug in TO. There's nothing wrong with TRS2004 or the asset and reinstalling either won't change anything.
The problem is caused by Trainz Objectz taking the first "kind" tag it finds in a config.txt file, even if it is inside another tag.
The asset does not need to be fixed in order to be fully operative in TRS2004, but if it is desired to solve the problem in Trainz Objectz then in the asset's config.txt file move the real "kind" tag to near the start of the file, perhaps just below the kuid tag. Be careful not to corrupt the first line of the config.txt file. Then shut down and restart Trainz Objectz to check that the spurious "nd" category has disappeared.
If you're not confident editing config.txt files, or if you don't understand their tags and curly brackets structure, then I suggest that the good old principle of "if it ain't broke don't fix it" applies.
HTH, John