Hi Mick!
The solution to this exact problem is actually pretty easy, but the background for the problem is a bit harder to come by. Let's start with the solution!
I've just tried "The Xfiles", and that works wonderfully. I know filenames won't look that great, but after all, we use Mizuu to get rid of filenames and look at content instead :-)
The reason why "The X-Files" won't work is that Mizuu considers '-' as a space. Many filenames use the character as space between words or tags, i.e. "The Big Bang Theory-S01E01.mkv". Here it is used as a separator between the show title and the episode number and season number.
I'm always trying to do the best I can at my end of the table by optimizing Mizuu and improving its "intelligence" with regards to filenames and such, but I'm also certain that the TV database, Mizuu is using, will improve its ability to recognize titles - with and without various characters.
Hopefully that helped a bit. Sorry about the inconvenience, and I do hope that you're otherwise happy with Mizuu :-)
Cheers,
Michell