Just updated to the latest Garmin Express 18.104.22.168 and the new feature is a regular crash "Garmin Express quit unexpectedly" You can reopen the application..... and each time it does it again. Marvellous. Have reported it.
It's exactly what happens to me after the last Garmin Express update (using MacOS Mojave 10.14.5). I am unable to open Garmin Express without quitting unexpectedly.
After a complete Garmin Express uninstall it only works the first time you open it after a fresh install. Then, as soon as you close it and try to reopen, it quits again every time.
Several days with the same problem without any update or even a message from Garmin: very disappointing!