At the moment, this particular Mac problem has me totally stumped. It only affects one Mac, and doesn’t seem to affect the day to day operation of the computer, it only seems to affect one particular dialog, and even then the dialog works perfectly okay, it just looks a bit odd.
The problem is that when I run an installer, if the installer needs elevated permissions in order to install, the dialog asking me to enter my password comes up like this:
What appears to be happening is the variable bits of text on the dialog are being put in in what appears to be arabic, if I enter my password it all works fine. Run the same installers on another Mac and the dialogs come up properly. It may well be that I’ll need to do a clean install of MacOS and rebuild the computer from a backup, but I’d rather work out what’s caused it in the first place!
I have the same question open on the Apple Stack Exchange site also.