I don’t know whether you have noticed this or not, but when you run many different Mac Utility Apps they usually have a feature that cleans the “font cache.” The reason for this is corrupt or malfunctioning Fonts can cause all kinds of problems on your Mac. I think font problems were worse in days gone by, but fonts can still be a problem. It is a good idea to do a little maintenance on Fonts from time to time. The macOS has a built-in font problem catcher in the Font Book App.
The Font Book App has been around on the Mac for quite a while. People who do serious design work use a third party Font Management App like Suitcase or FontAgent Pro, there are others. However, for the rest of us the built-in Font Book App is adequate to manage our Fonts.
When you open Font Book you get this window listing your Fonts:
To check for any Font problems, do a “Select All” on your Fonts list and choose Validate Fonts from the File Menu:
Font Book will check all your fonts listing any problems:
When it is finished it will provide a full list of Font problems like so:
Here is my policy on Font issues. If Font Book marks a font “serious error” I go ahead and remove it, no questions asked. It is not worth the grief that font could cause. To remove the font, put a check mark by it and click the “Remove Checked” button. You will get this warning:
The macOS is being careful, sometimes Fonts can cost a lot of money. When you click “Remove” that font is gone from your system.
The Validation process will also list what is calls “minor problems”:
Here is my policy for “minor problems.” I will scroll through the validation list and locate each font listed as a minor problem and review it. If it is a font that I have never or will never use, I remove it. If it is a font I am using for something important I may leave it or scroll through my fonts to find a substitute that is close to the problem font. I will remove the problem font and use the substitute.
Have you looked in Font Book lately to see how many fonts are installed on your machine? I think you will be amazed at the number of them. It seems like every time that you install an App it has to install some fonts. This leads me to a suggestion regarding your fonts. It might not be a bad idea to scroll through your list of fonts in Font Book and remove ones you know you will never use (Japanese fonts anyone?)
You do not need to do maintenance on your Mac Fonts very often, but it does not hurt to at least do the validation process once or twice a year. Font issues are so difficult to detect while using Applications, so it is a good idea to try to head them off at the pass.