If you have Windows 11 24H2 then its possible you’re experiencing the Samba issue others are experiencing (since May 2024). Microsoft apparently made a change to its Samba (SMB) protocol in Windows 11 that is causing some issues. Some suggested workarounds in the following Microsoft link:
PS: Another possible suggested fix, even though it references slow SMB speed, is mentioned in the following link:
Other possible suggestions are to change the SMB version in the My Cloud Dashboard > Settings > Network > Windows Services section. Or possibly even editing the My Cloud smb.conf file using SSH to specify specific SMB min and max versions to be used.