Inquiry Regarding Update Rollback (Undoing changes) from Build 26200.7840 to Build 9168

Question

Dear Microsoft Support Team,

Good day.

I am writing to seek technical clarification regarding a recurring update failure we are experiencing on Windows 11.

During the installation of Build 9168 on a system currently running Build 26200.7840, the update process consistently fails and triggers the "Undoing changes" rollback sequence. Even after attempting standard offline in-place upgrades via ISO and isolating background processes through a Clean Boot, the system reverts back to the original build without error codes logged clearly during the active GUI phase.

Could you please advise on the following:

Is there a known version conflict or servicing stack constraint that prevents upgrading directly from Build 26200.7840 to Build 9168?

Are there specific prerequisite packages, registry parameters, or component store resets (such as extended DISM commands) required to bridge this build gap successfully?

Thank you very much in advance for your technical support and guidance.

Best regards,

Kriangkai Ketsakul (Tom)

Answer 1

Dear Microsoft Support Team,

Thank you for the clarification and guidance.

I have attached the setuperr.log file for your review. Unfortunately, I am unable to attach the setupact.log file due to its large file size.

Based on the previous log analysis, the error occurs during the finalization/migration phase with the error code 0x8007042B, and it seems related to msctfmig.dll (CCSIAgent). Could you please check why the update is failing and advise on how to resolve this?

Thank you for your support.

Best regards,

Tom

Answer 2

Hi Tom,

Build 26200.7840 and 26200.9168 are both Windows 11 version 25H2 builds. Build 26200.9168 is the August 2026 cumulative update KB5121003, so there is no documented requirement to install every intermediate build before updating from 26200.7840.

Since the installation reaches “Undoing changes” even with an ISO/clean boot, I recommend checking the actual setup failure rather than repeatedly resetting Windows Update.

Please check these logs after the rollback:

C:\$WINDOWS.~BT\Sources\Panther\setuperr.log

C:\$WINDOWS.~BT\Sources\Panther\setupact.log

C:\Windows\Logs\CBS\CBS.log

You can also run SetupDiag, which can identify many common upgrade-blocking errors from the setup logs.

There is normally no special registry change or extended DISM procedure required simply to move from 26200.7840 to 26200.9168. Microsoft also confirms that the latest servicing stack is combined with the cumulative update.

If possible, please share the last relevant errors from setuperr.log or the SetupDiag result. That should help identify whether the rollback is caused by a driver, compatibility block, servicing/component-store issue, or another setup failure.