Quick Answer
Open Regedit, go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters, create a DWORD named SessTimeout, set it to decimal 120 (or higher), and reboot. That's it.
Why This Happens
You're copying files to a network share, running a backup, or printing to a network printer, and bam—the operation stops with ERROR_TIMEOUT (0X000005B4). I've seen this more times than I can count. Last month, a dental office had their X-ray software hang every afternoon because their NAS took too long to respond. The default SMB timeout on Windows is 60 seconds. If the server or NAS is slow—say it's under load, has a flaky switch, or is a cheap consumer drive—you'll hit that window.
This isn't a corrupt file or a broken driver. It's Windows giving up too early. The real fix is telling it to wait longer.
Fix Steps – Increase the SMB Timeout
- Open Registry Editor. Press Win + R, type
regedit, hit Enter. - Navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters - Create a new DWORD: Right-click in the right pane, choose New > DWORD (32-bit) Value, name it
SessTimeout. - Set the value: Double-click
SessTimeout, select Decimal, and type120(that gives you 2 minutes). For really slow servers, go up to 180 or 300. - Reboot your PC. Or restart the Workstation service from an admin command prompt:
net stop lanmanworkstation && net start lanmanworkstation.
Test your operation. If it still times out, bump the value higher. I had one client with a 2008 R2 server that needed 300 seconds to sync their inventory files.
Alternative Fixes If That Doesn't Work
Check the server or device
If upping the timeout to 300 doesn't help, the problem isn't on your end. The server is too slow or dropping connections. Plug a laptop directly into the same switch and test. If you still get timeouts, it's the server's hardware or network.
Disable SMB packet signing (temporarily)
SMB signing adds overhead. If your server is ancient (Windows Server 2003 or a low-end NAS), turn it off on the client. Run this as admin:
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters" -Name "RequireSecuritySignature" -Value 0 -Type DWordReboot. Warning: this lowers security. Only do this on a trusted network. Undo it later by setting the value back to 1.
Check for antivirus interference
I've seen McAfee and Norton scan network files mid-transfer and kill the connection. Temporarily disable real-time scanning for network traffic. If the error stops, add an exclusion for the server's IP or UNC path.
Update network drivers
Realtek and Broadcom NICs on older Windows 10 builds had a bug where large file transfers would timeout. Update the driver from the manufacturer's site—not Windows Update. I fixed a call center's entire print queue by updating the NIC driver on their print server.
Prevention Tip
Don't rely on the default 60-second timeout. If you regularly work with slow network resources—backup servers, NAS units, remote offices over VPN—set SessTimeout to 120 or 180 right after a fresh Windows install. I do this on every new setup I build. Takes 30 seconds, saves you a headache later. Also, replace old 100Mbit switches. That's usually the real culprit causing the delay.