Ok I've got a weird one.
The "Metadata API Version Checker" seems to be going rogue.
As I type in this file, duplicate lines are showing up. I was able to get the entire page full of these lines a few minute ago.
I updated IntelliJ and all Plugins, restarted PC, restarted IntelliJ. I can only get a max of 3 to show up now, but still indicates some kind of gremlin.
I'm guessing this is an IC issue and not SF, but let me know if I'm wrong.
Thanks!