Windows Updates failing after upgrading to Windows Server 2025 Core

My Homelab consists of 4 Windows Servers. They were all initially running Windows Server 2019 (2 GUI, 2 Core) which were at some point upgraded to Windows Server 2022 and then again to Windows Server 2025.

After the latest in-place upgrades to Server 2025 my two GUI based installs had no problem installing Windows Updates in January and February. My two Core based installs would both fail to install updates.

When I tried to install this February’s KB5051987 this month it would fail with the following:

2025-02-12 11:13:43, Info                  CBS    Exec: Processing complete.  Session: 31161729_1978236699, Package: Package_for_RollupFix~31bf3856ad364e35~amd64~~26100.3194.1.13, Identifier: KB5051987 [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:13:43, Info                  CBS    UpdateReserveManager available; finalizing reserve adjustments...
2025-02-12 11:13:43, Info                  CBS    Removing the pending hard reserve adjustment for Client: UpdateAgentLCU, Session: 31161729_1978236699
2025-02-12 11:13:43, Error                 CBS    Failed to perform operation.  [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]

I got the same thing last month with January updates but figured the issue might just be that Server 2025 was brand new at the time and Microsoft borked something with the January update for Server Core.

My first assumption was it was this old issue from Server 2019 happening again. Tried the script from the post but it couldn’t find anything to fix in the CBS log.

Digging through the CBS.log file (C:\Windows\Logs\CBS\CBS.log) I came across this:

2025-02-12 11:44:42, Error                 CSI    0000000c@2025/2/12:19:44:42.899 (F) onecore\base\wcp\componentstore\csd_locking.cpp(97): Error STATUS_SXS_ASSEMBLY_MISSING originated in function CCSDirectTransaction::LockComponent expression: (null)
2025-02-12 11:44:44, Error                 CSI    0000000d (F) STATUS_SXS_ASSEMBLY_MISSING #397662# from CCSDirectTransaction::OperateEnding at index 0 of 1 operations, disposition 2[gle=0xd015000c]
2025-02-12 11:44:44, Error                 CSI    0000000e (F) HRESULT_FROM_WIN32(ERROR_SXS_ASSEMBLY_MISSING) #397432# from Windows::ServicingAPI::CCSITransaction::ICSITransaction_UnpinDeployment(Flags = 0, a = Microsoft-Windows-Internet-Naming-Tools-Deployment, version 10.0.26100.1882, arch amd64, nonSxS, pkt {l:8 b:31bf3856ad364e35}, cb = (null), s = (null), rid = 'Microsoft-Windows-Internet-Naming-Tools-Package~31bf3856ad364e35~amd64~~10.0.26100.1882.WINS-Server-Tools', disp = 0)[gle=0x80073701]
2025-02-12 11:44:44, Info                  CBS    Failed to unpin deployment for Update 'WINS-Server-Tools' [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Info                  CBS    Failed to execute item[0] in Package: Microsoft-Windows-Internet-Naming-Tools-Package~31bf3856ad364e35~amd64~~10.0.26100.1882, Update: WINS-Server-Tools [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Info                  CBS    Failed to execute execution update. [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Info                  CBS    Failed to execute execution package: Microsoft-Windows-Internet-Naming-Tools-Package~31bf3856ad364e35~amd64~~10.0.26100.1882 [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Info                  CBS    Failed to prepare execution [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Info                  CBS    Failed to execute execution chain. [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:44, Error                 CBS    Failed to process single phase execution. [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:46, Info                  CBS    Reporting selectable update change for package: Microsoft-Windows-Internet-Naming-Tools-Package~31bf3856ad364e35~amd64~~10.0.26100.1882, update: WINS-Server-Tools, start: Staged, applicable: Absent, target: Absent, client id: DISM Package Manager Provider, initiated offline: False, execution sequence: 329, first merged sequence: 329, download source: 0, download time (secs): 0, download status: 0x80073701 (ERROR_SXS_ASSEMBLY_MISSING),reboot required: False, edition based selectable: False, overall result:0x80073701 (ERROR_SXS_ASSEMBLY_MISSING)
2025-02-12 11:44:46, Info                  CBS    Exec: Processing complete.  Session: 31161734_2240362135, Package: Microsoft-Windows-Foundation-Package~31bf3856ad364e35~amd64~~10.0.26100.1, Identifier: Windows Foundation [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:46, Error                 CBS    Failed to perform operation.  [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]
2025-02-12 11:44:46, Info                  CBS    Session: 31161734_2240362135 finalized. Reboot required: no [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]

The key line was Failed to unpin deployment for Update 'WINS-Server-Tools' [HRESULT = 0x80073701 - ERROR_SXS_ASSEMBLY_MISSING]

Why on earth was Windows Server trying to do anything with WINS? I’ve never deployed it in my Homelab and it is exceptionally obsolete. Oddly the error message was the same on both Core servers in my Homelab.

Did a quick check and nothing WINS related was installed:

PS C:\> Get-WindowsFeature | Where-Object { $_.Name -like "*WINS*" } | Select-Object Name,DisplayName,InstallState
Name      DisplayName       InstallState
----      -----------       ------------
RSAT-WINS WINS Server Tools Available
WINS      WINS Server       Available

I tried all the standard DISM /online /cleanup-image blah blah commands you find all over the internet with SXS errors, nothing helped.

I figured I’d install/remove the WINS Server Tools and that might correct whatever was going on… but installing it failed using the Core machine as a source and a working Server 2025 GUI install as a source:

PS C:\> Install-WindowsFeature -Name RSAT-WINS -Source "\\WORKING-SERVER-2025-GUI-SYSTEM\c$\Windows\WinSxS"
Install-WindowsFeature : The request to add or remove features on the specified server failed.
Installation of one or more roles, role services, or features failed.
The referenced assembly could not be found. Error: 0x80073701
At line:1 char:1
+ Install-WindowsFeature -Name RSAT-WINS -Source "\\cayenne-02.nom.fizi ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (@{Vhd=; Credent...Name=localhost}:PSObject) [Install-WindowsFeature], Exception
    + FullyQualifiedErrorId : DISMAPI_Error__Failed_To_Enable_Updates,Microsoft.Windows.ServerManager.Commands.AddWindowsFeatureCommand
Success Restart Needed Exit Code      Feature Result
------- -------------- ---------      --------------
False   No             Failed         {}

Even stranger, after that failure the feature disappeared from the server all together:

PS C:\> Get-WindowsFeature | Where-Object { $_.Name -like "*WINS*" } | Select-Object Name,DisplayName,InstallState
Name DisplayName InstallState
---- ----------- ------------
WINS WINS Server    Available

The CBS log still only provided the same error message as earlier when I was trying to install Windows Updates.

Some more random searching on the internet lead me to a unrelated forum post where someone suggested mounting the Windows Server 2025 ISO and performing a repair installation. So I did… and it worked. After running through the repair install on both systems they now patch without issue.

When I did my in-place upgrades I used the first release of the trial ISO that Microsoft provided for Server 2025. My best guess is that ISO was half-baked or corrupted some how. Sorry I deleted it before I thought to make get a SHA256 hash of it.

I did the repair using the OEM ISO:

Filename: X23-81958_26100.1742.240906-0331.ge_release_svc_refresh_SERVER_OEMRET_x64FRE_en-us.iso
SHA256: 854109e1f215a29fc3541188297a6ca97c8a8f0f8c4dd6236b78dfdf845bf75e
SHA1: a46f8b2097d1f01e9be05e9c059862c3c7d5fdcb