I use Libre Office, and the other day I wanted to see what a piece of text would look like with line spacing 1,5 as opposed to single.
I used "Paragraph" under "Format". I didn't like it, so I changed it back to single, saved it.

But .. each and every time I open that file, it will be displayed in 1,5 line spacing :/
Other files I got, open normally, in single line spacing. It's just that one file that somehow seems to hold a setting, and I don't know how to change it.

Anyone have a clue as to what went wrong?

operator error
(it's the loose nut between the computer desk and the office chair)

Could you be more specific, I can't find that nut? Been on my knees under the desk even ... nothing?

Sorry Crystal I've never used Libre. Only think I can think is it may be something in your options. You could try copying into a new document where you've already set it up how you want it.