I've been battling a particularly stubborn issue on a Windows Server 2008 R2 system where my elevated domain account gets locked out 10-12 times daily. Through extensive troubleshooting, I've traced the lockouts to failed Group Policy update attempts occurring approximately every 90 minutes.

Three distinct events appear in the System log during each lockout cycle:

Event ID 14: Credential Manager password validation failure
Event ID 40960: Kerberos authentication failure (0xc0000234)
Event ID 1058: Group Policy processing failure

Despite Event ID 14 suggesting Credential Manager issues, exhaustive checks reveal:

• No stored credentials in Credential Manager
• Problem persists regardless of Credential Manager service state
• Occurs even after profile deletion and recreation

The key error shows Kerberos failing with status 0xc0000234 (account locked due to excessive bad attempts). Network captures reveal the server attempts to authenticate using stale credentials during gpupdate.

Here's how to reliably reproduce the issue:

1. Ensure account is unlocked
2. Run gpupdate /force
3. Immediately check account status (shows locked)

After weeks of investigation, I discovered this occurs when:

• The server's computer account password is out of sync with AD
• Stored Kerberos tickets become invalid
• The system attempts to use cached credentials for GP updates

Here's the complete resolution process:

# First, reset the computer account in AD
Reset-ADComputer -Identity "ServerName" -Server "DCName"

# Then on the affected server:
netdom resetpwd /server:DCName /userd:DomainAdmin /passwordd:*

# Follow with a restart of both the server and KDC service
net stop kdc
net start kdc

To avoid recurrence:

1. Implement regular computer account password rotation
2. Monitor for Event ID 1058 occurrences
3. Consider upgrading from Server 2008 R2 (EOL)

Here's a PowerShell snippet to help diagnose similar issues:

function Test-GPLockout {
    param(
        [string]$ServerName,
        [string]$UserName
    )
    
    $lockoutStatus = (Get-ADUser $UserName -Properties LockedOut).LockedOut
    Invoke-Command -ComputerName $ServerName -ScriptBlock { gpupdate /force }
    Start-Sleep -Seconds 5
    $newStatus = (Get-ADUser $UserName -Properties LockedOut).LockedOut
    
    if ($newStatus -and !$lockoutStatus) {
        Write-Host "Lockout occurred after GPUpdate!" -ForegroundColor Red
        Get-WinEvent -LogName System -MaxEvents 20 | 
            Where-Object { $_.Id -in @(14,40960,1058) } |
            Format-Table -AutoSize
    }
}

When your elevated account gets locked 10-12 times daily after running gpupdate on Windows Server 2008 R2, you're facing one of those AD mysteries that makes even seasoned admins scratch their heads. The key symptoms manifest in three distinct event logs:

# Sample Event IDs triggering the lockout
Event 14: Credential Manager password validation failure
Event 40960: Kerberos authentication error (0xc0000234) 
Event 1058: Group Policy processing failure

The root cause lies in the server attempting to authenticate using stale credentials when accessing \\contoso.com\SysVol. Here's how to verify the Kerberos ticket behavior:

# Check current Kerberos tickets
klist tickets

# Force ticket renewal (run as elevated user)
klist purge
gpupdate /force

This often reveals expired or conflicting tickets when accessing domain controller resources. The server keeps retrying with cached credentials until account lockout threshold is hit.

Add these registry tweaks to prevent credential caching issues:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa]
"DisableDomainCreds"=dword:00000001

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters]
"BasicAuthLevel"=dword:00000002

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CredentialsDelegation]
"AllowProtectedCreds"=dword:00000001

When all else fails, resetting the computer account often resolves underlying authentication issues:

1. On DC: Get-ADComputer -Identity "ServerName" | Reset-ADComputerMachinePassword
2. On affected server: Test-ComputerSecureChannel -Repair
3. Reboot server and verify with: nltest /sc_verify:contoso.com

Implement these Group Policy settings to avoid recurrence:

<GroupPolicy xmlns="http://www.microsoft.com/GroupPolicy/Settings">
  <Computer>
    <SecurityOptions>
      <NetworkSecurity_RestrictNTLMInDomain>1</NetworkSecurity_RestrictNTLMInDomain>
      <NetworkSecurity_LanManagerAuthenticationLevel>5</NetworkSecurity_LanManagerAuthenticationLevel>
    </SecurityOptions>
    <CredentialsDelegation>
      <AllowProtectedCreds>1</AllowProtectedCreds>
    </CredentialsDelegation>
  </Computer>
</GroupPolicy>

Remember to monitor lockout events using:

Get-WinEvent -FilterHashtable @{
  LogName='Security'
  ID=4740
} -MaxEvents 10 | Format-List