My project just had this same error code, and I was able to get the private version uploaded by deleting a few unused audio files that I had pulled in. The audio files were taken directly from the folder of music licensed by Epic Games though, so I still don’t really understand the bug.
I cannot publish this version however because “There are items in this private version which have previously failed moderation”… so I guess I am stuck?
Link to the website for downloading the audio files:
Box