It seems you cannot find anything in the Audit logs , Have you checked the Event Viewer for any trace?
If you cannot find anything in Event Viewer I would suggest you use tools like Procmon to find the root cause for this behaviour.
On the target computer, check the local security policies (secpol.msc) to ensure that user rights assignments and privileges are correctly configured. Look for any policies that might be blocking the necessary privileges.
If you experience the “a required privilege is not held by the client” issue while trying to copy a file to the root folder, you can try to fix it by copying the particular file with Command Prompt.
Step 1: Press Windows + R to open the Run dialog. Type cmd in the text box and then press Ctrl + Shift + Enter to open the elevated Command Prompt.
Step 2: Type copy [address of the source file] [Destination address] in the panel and press Enter.
Hope this resolves your Query !!
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