New TextEdit "Untitled" documents use only odd numbering

I am experiencing a very strange bug with TextEdit.

I would even call it odd (double pun very intended).

Whereas new "Untitled" documents should open with the default name "Untitled," "Untitled 2", "Untitled 3," etc., my system only uses odd numbers. Thus, the first new document is called "Untitled," but the second is "Untitled 3," and the third is "Untitled 5."

I'm sure there's a corrupted configuration file or something along those lines, but I don't know where that would be or how to fix it.

Screenshot for evidence:

Any help would be greatly appreciated!

I am running MacOS Sierra 10.12.5 on a 2015 Retina MBP.