Why do I get 2 of the same name album folders for one album

Hey!
When I tag a full album of mp3s and put it on my MP3 player I get two folders of the album with the same name. The number of tracks is divided between both folders??
Why does this happen? I've double checked all of the spelling. Thanks!

How exactly do you "put" your album of mp3s on your MP3 player?
Directly from Mp3tag? With an Action?
Manually with Drag & Drop from the Windows File Explorer?

Please supply a screenshot from the extended tags dialogue Alt-T for a single file that goes to the first folder and also a screenshot from a single file that goes to the second folder.

In general: MP3tag does not create folders on its own.
So I think there was an existing folder on the player and you added another one.
I also doubt that 2 folders could have the same name.

One of your duplicate folder names probably has a space at the beginning or end.

MP3Tag removes this space when tagging your files, thus creating the apparently duplicate folder name.