There is no way to replace files in the UBB cp other that going over every screen and re-saving them.
Yes UBB now makes a backup of config.inc.php.
So you could rename it.
But if you have no confidence in that file then.
It would be best to upload a copy.
You will need to use ftp and upload the files.
Using the clear cache may help while doing so.

As I said before maybe you host edited them during a maintenance. upgrade.

By coincidence I have a site that the .htaccess file and php.ini file was edited just this past week and broke the forum.
There was evidence that a backup file was created but they were both incorrect.

Last edited by Ruben; 07/27/2020 4:23 PM. Reason: Added Comment

Blue Man Group
There is no such thing as stupid questions. Just stupid answers