When I edit and save this file I'm getting a couple of warnings:
MySource Warning
File: [SYSTEM_ROOT]/core/include/locale_manager.inc Line: 504
Message: File Belongs to different Repository [FVER0008]
Backtrace: Show
MySource Warning
File: [SYSTEM_ROOT]/core/include/locale_manager.inc Line: 504
Message: Error occurred getting file information, unable to run upToDate() [FVER0002]
Backtrace: Show
Is there something I can do to fix
It means that your system has moved filesystem path, but the system_move_update.php script hasn't been run.
You need to run:
php scripts/system_move_update.php /var/www/path/to/matrix
This script will prompt you to enter the old system root path. It will update all the files in the repository to point to the new path.
If you don't know the old filesystems paths, you can find them using this command (run this from the Matrix system root):
find data -type f -path '*/.FFV/*' |xargs head -qn1 |sort |uniq