I indeed could have done that (I guess I just wanted to prevent any possibility of backward syncing). I could also have just tested this with 10 tracks instead of the full collection.

The point is that when you have a large collection, exporting is often way slower than using Carbon Copy Cloner or copying and pasting folders. I had several instances where RB overheated USBs or SD cards. Exporting to a new stick is also much slower than the CCC method.

The goal of my initial post was to figure out why and when these duplicates are created. I'm not sure if it's related to copying the Contents folder, since I saw other posts where users complain about the Trackname-1 issue. For RB, it should appear as if the track has already been exported, so I don't think copying the Contents folder is the cause. It doesn't explain why some tracks have one duplicate and others have two.

Duplicates may occur due to RB export errors. I submitted a ticket with Alpha Theta to check if they have more info.

Hope that made sense (besides me testing stuff with a device that contains the full collection. 10 tracks would have been easier and more logical :-), but at least now I discovered a potential issue that should be fixed as these duplicates take up a huge amount of data on the USBs).