Hi,
Based on my experience, this error may due to the Server 2008R2 miss updates, please check if the Server 2008R2 has installed the latest windows update, if not, please check the following article about how to update Windows Server 2008R2:
Below is the link about the known issue of Storage migration on Server 2008R2:
https://learn.microsoft.com/en-us/windows-server/storage/storage-migration-service/known-issues
And the following is a similar issue with yours:
Thanks for your time!
Best Regards,
Anne
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