@carlwgeorge thanks for the report, however none of the stack traces in your paste contain anything related to mkvtoolnix. Also, mkvtoolnix can't possibly be able to crash gnome-shell directly. I think it just exposed a bug in either gnome-shell or one of the drivers. Please report the crash via abrt (System Tools -> Problem Reporting) if possible. Does it happen only under Wayland or under Xorg as well? Does it happen with any other desktop environment?