Easy fix!
Change the path again to "Blank" I mean backspace everything in the path
Exit Trainz completely, if you are running Trainz on Steam make sure that Trainz has stopped automatically
Relaunch Trainz, a new database will be created
Exit Trainz completely
Move over your original content build xxxxxxxxxx folder "Local, Packages and Original" and place these folders into the new build xxxxxxxxxx folder
launch Trainz and rebuild database, now! depending on your content I would advise do not attempt to "Start Trainz" during the database repair, let nature take its course
Once you have rebuilt the database, you can delete all old build xxxxxxxxxxx folders
If you are a route builder, please keep backups of the backups folders *