This combination of a 410 error and a terminated request body strongly suggests an issue with the Wasabi S3 service configuration, rather than with your PowerShell code directly. It's also possible the part size is too large.

By systematically checking credentials, S3 key names, and the object state, we can isolate and address the root cause.

If the problem still persists after these modifications, I suggest consulting Wasabi support again and providing them the full verbose error logs, and the code snippet you're using.