Witgui runs on top of the wit/wwt command line tools. When an error occurs or something doesn’t behave as intended with the generated game files, it can be useful to inspect the output of these tools and/or get help on the official support forum: https://gbatemp.net/threads/wwt-wit-wiimms-wbfs-iso-tools.182236

  1. Open the Terminal (in /Applications/Utilities).
  2. Copy and paste “/Applications/Witgui.app/Contents/MacOS/Witgui -log” into the Terminal and press Enter.
  3. A new app instance will open. Reproduce the issue.
  4. A bunch of lines will appear inside the Terminal that contain some logs.
  5. You can quit Witgui and the Terminal now.