Downgrading WordPress to version 5.4.2 is the only thing that fixed it for me. Go here to get an archived WordPress version release: https://wordpress.org/download/releases/

I tried these before downgrading: disabling all plugins, disabling mu-plugins, disabling web browser add-ons, testing in both Firefox and Chrome (latest versions). None of this had an impact, but as soon as I downgraded WordPress, it worked.

• This reply was modified 4 years, 3 months ago by mjm-design. Reason: typo