Can't edit stylesheet in "Edit Stylesheet"

Update: resolved!

I think this is a bug? Yesterday, Theme > Edit Style sheet was working just fine. Right now, I just see this:

https://i.postimg.cc/KvHNyt62/image.png

And I can't edit it at all. It's not acting as a text box. I can copy/paste the words that are written down, but I can't interact or change them at all. I also can't scroll, not even with my arrow keys.

I'm on W11, using Opera GX (fully updated).