On Catalina 10.15.7, Glyphs version 3.0.4 (3108) crashes when opening old files created with Glyphs 2.6.8 (1360). All other files open up nicely. It just shuts down, no error dialog comes up, only the “Glyphs quit unexpectedly” notification.
Files that cause the crash have the date in correct format, for example:
date = “2019-06-19 22:58:30 +0000”;