Exception occurred when creating MZContentProviderUpload for provider. (1004)

For me just log out on Web iTunesConect / AppsoreConnect portal.

Quit Xcode (if Possible restart) and then upload the build.

If you close all the other app and upload build in sylo makes a job easy.

Also using the "Application Loader" is a Good Solution!

It seems like a temporary issue with apple. Trying few times to send worked and the upload was successful.