Actually this error existed also in TrueCrypt and it happens when you wrongly set the two favorite to have the same slot!
This is a typical mistake and it happens when user mount a volume in a slot, adds it to favorites, dismount it and then mount another volume to the same slot and then adds it to the favorite.
Although it is not displayed in the dialog for managing favorites, the slot number used when you click "Add to favorites..." is written to the favorites XML file and it is this value that is used during mount operation.
You can read the content of the XML file which is located:
- For TrueCrypt: "/Users/YOURNAME/Library/Application Support/TrueCrypt/Favorite Volumes.xml"
- For VeraCrypt: "/Users/YOURNAME/Library/Application Support/VeraCrypt/Favorite Volumes.xml"
If you follow the sequence I described above, you can easily reproduce the issue in TrueCrypt.
That being, VeraCrypt should check for such duplication issue and refuse to add the favorite to the list after informing the user. I'll see if I can implement this check before the final 1.12 is out.