that sounds super annoying—sorry you're dealing with it! A few things you could try: clear your profile data or create a new one in case there’s a corrupted setting, check for conflicts if you’re using both Firefox’s password manager and a third-party one, and make sure to fully reinstall Firefox, including removing the profile folder.

I did all the things again, but your comment got me thinking that I should uninstall firefox developer edition too. So I did that and did a system search for all files with firefox in the name and deleted those as well. Now it seem to be working!