Edit: Bump! Seemed that maps not work in Desmume or No$Gba....Working on it...
Yes, i have the same error.
It doesn't work on real DS too.
Viewers are not completely accurate, they can display all errors and corrupted polygons.
You can't add manually a polygon, it's too complex.
But... you can only use a tool like Autodesk and compare all bytes after reinsertion.
Maybe that can help you.