Final cut pro x crashes by exporting a frame

Do please post an Etrecheck report as LocaAlicia requested.

Also: whenever the application crashes, delete its preferences, as they become corrupted and that may cause other subsequent crashes. To delete preferences, hold down command and option while starting the application and click Delete Custom Settings. The application will start with default settings and open an "Untitled" library. Adjust the settings, reopen the library you were working, and see how it works now.

Create an EtreCheck report →Paste it into Add Text