How do you fix texture errors when the textures are encrypted and the pev tool can't fix them? This happens when moving files by cdp into Trainz like packaged or payware. Do you have to find out what package the assets came from and download the package (route) the right way? Why would N3V make some assets unusable in newer Trainz versions simply because of more strict error checking, etc.?
I mean simple assets like buildings, grass, trees, etc. when they have texture errors after importing them by CDP instead of the right way through a package install.
You give the answer to your own question:
Use the right way through a package install.
No if's, no but's, just that.
There are some errors in built-in stuff and some payware. The game ignores those when they come from those sources (built-in or package installs), but they will show up when you start exporting and importing them via CDP's. There is no reason to do that if you legally own that content as you can just download it in your new game again AFAIK.
... The game ignores those when they come from those sources (built-in or package installs), but they will show up when you start exporting and importing them via CDP's....
Yup.
I don't agree with N3V's choice in this, but that's how they do it.
Though I do understand why: Saves them having to fix old (as it usually is old) content.