It probably isnt the code. When something fails content review it wants you to fix the problem and upload a new version. The problem is the rejection reasons are often vague.
Changing your code will have been enough to generate a fresh private island code and submit that. It would also have done the same if youd moved one prop though. It just needed a change enough to make a new private code.
As for why it failed content review the first time? Sometimes different moderators see things differently and one will pass something another rejects.