Notice that space after the word "hill". To get rid of that blank space I wrote this:
Actions / Replace "_FILENAME": " .mp3" -> ".mp3"
When I run the action in Mp3tag v2.41 it changes on screen but if I then double click on the song it says "can't be accessed". Mp3tag then refreshes the directory and the mp3 has reverted back to "John Silver - On The hill .mp3"
Is this a bug or should I write a different formula?