It requires enabling more error notification from PHP which is suppressing the error to figure out what is actually happening. But sounds like th error may expose sensitive path information or database information and hidden. Unless they suppress all errors on MediaWiki. I'm not sure. Honestly never seen this sort of vague error without more information for the web staff.
Still, to prevent phishing and leaking of sensitive path structures that could be used in attacks it might be best to lock down the server to the admins IP address or range, and than do the edit and error checking and fixing.