Greasy Fork

Great, but unfortunately doesn't remember the settings :(

That's strange. When does it usually forget them?

It mostly happens when I close the browser for some reason.

Maybe you changed some privacy settings in your browser? Gplex saves settings with localStorage, so anything that messes with localStorage would probably be causing it. Perhaps if you have your browser set to clear browsing history on close, it might also clear Gplex's settings (though I'm not sure about that, I never tested it). If you put a user.js file in Firefox (these are also usually made for privacy purposes), they might also be messing with it.

If it's not that then I have no idea.