I found one issue in that the Transporter seems to key off the bundle signature and only allows one upload at a time - maybe per account.
We have two app variants that share the bundle ID, they have to be processed sequentially.
We have two app variants that share the bundle ID …
Why are you doing that? In general, having two apps with the same bundle ID is a very bad idea.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"