@rl
For everyone's benefit: the crash the user is describing can be caused by a bad font being installed in the system.
When you install fonts on macOS, don't just put them in the font folder. Instead, drag them into FontBook because then the font will be analyzed for problems.
For example, one font that was causing a user trouble generated this dialog when dragged into FontBook.
If a font shows errors like this, it may cause Isadora to crash.
Best Wishes,
Mark