Return
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Title
Unable to preserve Document Set Content Type -
Description
Migrating a Library from SharePoint On-Prem to SharePoint Online is not preserving the Document Sets, instead they migrate as a folder. -
Cause
Duplicated Document Set Content Type, one of them is corrupted. -
Resolution
Go to Site Settings > Site Contet Types > Look for "Document Set" Content Type then deleted the corrupted Content Type.
Note: You can identify the broken Content Type by open it and checking the "Document Set settings" option is missing.