At https://en.wikipedia.org/wiki/File:College_Guide_Cover_no_date.png, we received an OTRS ticket from the copyright holder granting a license for this image. So I wanted to remove revdelete from the original January 19 upload and revert to that version.
I am an admin and so I see a blue struck out link where it says "02:06, 19 January 2015" and "01:34, 19 January 2015" that I can click on and am able to view the image. So we know that the file hasn't been lost. (That's how I retrieved the file to re-upload it.)
But if I hit the "del/undelete" button, uncheck "Delete file content", and enter the reason "OTRS permission was submitted - no need for the smaller version", then I get the error "[67f86f32] 2015-04-25 12:58:51: Fatal exception of type DBUnexpectedError".