How can I repair the system if macOS displays garbled text when using certain fonts?

In nearly all cases, this problem is caused by technical problems with Apple’s font registration server. It can be fixed by forcing this subsystem to rebuild its caches. Perform the following steps:

1. Verify if only a particular user account, or all user accounts are affected by this problem. Make sure you are logged in as the user who experiences the problem.
2. Open the pane Caches.
3. Select the sub-item Font Caches.
4. If only the current account is affected, select the item Clean font caches of the user…. If all users are affected, select the item Clean font caches of the user and the operating system.
5. Press the button Clean font caches.

Further information: The Pane Caches.