https://www.dropbox.com/s/ro9cfp63dphz3zl/Screenshot%202018-05-21%2018.01.13.png?dl=0

What could this mean for me? I can't interact with the player at all, but it does prevent me from building in that location.

Actually, I've found 5 of them on my map now.

Uh, I don't know what this might be. BNW only destroys characters, never create. I guess it's possible that another mod somehow cause a character to not be associated with a player when BNW attempts to destroy the player character, but even this seems weird.
This issue may be quite difficult to solve (unless you have a short mod list), and it's probably not directly related to BNW (i.e. caused by a combination of BNW and another mod, or simply caused by another mod entirely).

Not sure how I created them either. Never had anything like that happen. I did disable a mod or two, and it might've happened around the same time.

If this ever happens to somebody, you can use "/c game.player.selected.destroy()" [without quotes] to kill the player entity that your mouse cursor is over. I was able to kill all 9 of mine that were spawned without affecting my game at all.