You won't lose anything. In your broken install, click on the Launcher and Trainz settings. Click on the Install tab to display the build-folder that version uses. Jot down the name so you know what it's called. - this is the one with the word build followed by a bunch of numbers and letters.
When you reinstall, TRS19 will automatically create a new data folder, aka a build folder.
Once installed, open Trainz settings on the Launcher.
Click on Install tab
Click on the ... to open up a Windows Explorer window.
Browse for your previous build folder.
Click Select.
A quick process of updating tables will occur and you'll need to restart TRS19 again.
Close the Launcher and start up.
If all goes well, you'll see all of your previously installed content in Content Manager.
If this doesn't work as expected, meaning you still have that locomotive issue, there's another process we can try.