Hi,
It may be affected by many factors, including system settings, system resources usage, NAS device performance etc.
In general, you may reference below link for step-by-step troubleshooting and narrow down the problem:
What can I do when the file transfer via Windows (SMB/CIFS) is slow?
Note: Since the websites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.
I hope this helps! Please let me know if you need any further assistance.
Kind Regards,
Karlie Weng
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