We should at least figure out why it is happening. I'm curious to know why this unicode is breaking BSS and not allowing importation.
I extracted the .osz with 7 zip without any issue. There doesn't seem to be anything wrong other than those misformatted characters in the song artist and tags etc.
I removed the accented A from the song folder name and the song opens right up. I assume if the that character is removed from the .osz's filename it will import. Even if you change the song information in the difficulties, the folder name will not change. In order to have a fresh updated folder name, export as .osz, make sure to remove the weird character if it gets added back, and then drag it back in. This will duplicate your folder, so make sure to delete the version with numbers or remove it from the song folder.
If it doesn't submit after that point then it's a server side problem, not being able to open the .osz to replace it.