All of these things that you have reported are expected to occur when duplicating a map. Firstly, a build data registry file cannot be copied like a normal file and must be generated by running the “Build” command with the level open.
For the save problem, this is because a map cannot be saved without being loaded. When you duplicate this map, you’re still on the original and must load the new map in order to save it. The error received at 0:42 is a symptom of not doing this.
The error given at 1:34 is in the same vein. To load another level, all levels must be unloaded, it must be saved. To save it, it must be the active level, so if you were allowed to transfer to another level at this point, the newly created level would not be saved and then become unloaded, which would cause it to be effectively deleted.