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0x80070039SystemHigh

Error 0x80070039 — Unexpected Network Error (ERROR_UNEXP_NET_ERR) | Windows System Error Fix

Windows 11Windows 10Windows Server 2022Windows 8.1

What Does 0x80070039 Mean?

An unexpected network error occurred during a file sharing or network operation.

Real-World Causes

  1. 1Network connection dropped during a transfer
  2. 2SMB session timed out or was disconnected
  3. 3Network hardware failure (switch, cable, NIC)
  4. 4VPN connection instability
  5. 5Server-side crash during the operation

Symptoms

  • ⚠File copy to network share fails mid-transfer
  • ⚠Mapped drive becomes inaccessible suddenly
  • ⚠Large file operations over network fail randomly
  • ⚠Network applications lose connection

DIY Fix

Beginner-friendly steps you can try at home

  1. 1Check physical network connections (cables, Wi-Fi signal)
  2. 2Restart the network router and switch
  3. 3Reconnect the mapped network drive
  4. 4Disable large send offload on the network adapter

Advanced Fix

For experienced users and IT professionals

  1. 1Check Event Viewer on both client and server for network errors
  2. 2Capture a network trace with Wireshark to identify where the connection drops

Frequently Asked Questions

Why do large file copies over the network fail?
Large transfers are more likely to encounter transient network issues. Try disabling Large Send Offload (LSO) and TCP Chimney Offload in adapter advanced settings. Also consider using robocopy with /Z flag for restartable copies.

Related Error Codes

0x80070035Bad Network Path (ERROR_BAD_NETPATH)0x8007003ABad Network Response (ERROR_BAD_NET_RESP)

About the Author

Windows Troubleshooting Team

Verified against official Microsoft documentation and real-world diagnostic data. Error behavior confirmed across Windows 10, Windows 11, and Windows Server.