Never heard of this one before, so wouldn't be too quick to blame AC.
Any font inside square brackets is missing. You would see [Arial] if somehow Arial was uninstalled from your machine. ArchiCAD does not have or look for a font named DEFAULT, so [DEFAULT] suggests that the file or template might have come from someone who set that as the font name for something to key the user in to change it perhaps?
Yet, the locked translator font problem - as well as the switching fonts - surely indicates a font mapping problem on your Mac.
Googling on 'leopard font cache problems' shows that there are others with font problems.
Have you tried running Onyx (free) and cleaning the font caches? (And/or perhaps go to the Onyx Automation tab and run all maintenance and cleaning options?)
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB