It looks like those are in prefixes. You would have had to apply custom CSS for that. I would check the CSS and update it to Font Awesome 5. This isn't a bug.
Indeed, FA 5 is now used, which has a number of changes. It you made customizations that directly referenced things in the CSS, they'll need to be updated to use the FA 5 versions (such as different font names or characters).
Indeed, FA 5 is now used, which has a number of changes. It you made customizations that directly referenced things in the CSS, they'll need to be updated to use the FA 5 versions (such as different font names or characters).
That may point to a bad cache or perhaps files not being uploaded correctly. Check the file health check and resolve any issues that lists. If it doesn't list anything, then you may want to try clearing your browser cache (or any sort of reverse proxy cache).
