When something seems glitchy in Firefox, Resetting is an option to consider. I recommend backing up your Bookmarks and Saved Passwords before proceeding.
An easy way to do this if your reading this article on Firefox is to follow the instructions here: https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings.
Another explanation with images to help guide you visually: https://malwaretips.com/blogs/reset-firefox-settings/https://malwaretips.com/blogs/reset-firefox-settings/
Good Luck!