Windows 10: Buggy patch stalls testing of 20H1 preview

Microsoft puts the brakes on Windows 10 20H1 testing as it works on a fix for a flawed update.

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Microsoft is fixing an error in last Tuesday's security update that prevented testers from installing a preview of a Windows 10 feature update expected in early 2020.

Last week Microsoft pushed its first 20H1 build to testers in the Windows Insider program's Fast Ring, but the release of Build 18875 failed for some testers, who were unable to install the update and saw various errors messages. 

Windows Insider boss Dona Sarkar has now confirmed that last Tuesday's security update KB4495666 preview build 18362.53 was the source of the problem. 

"We have determined that there is an issue with the Build 18362.53 (KB4495666) Cumulative Update that was released early last week which has caused updates to Build 18875 to fail," noted Sarkar

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The core issue is a "migration failure" that happens as Windows 10 tries to update to the new build. 

The company is now working on a new cumulative update that will be applied on top of Build 18362.53, which needs to be installed before Insider testers can update to the last builds from the 20H1 branch. 

For now, Microsoft has stopped offering Build 18875 to Insiders on Build 18362.53 and has stalled the release of new 20H1 builds until it unblocks the release for testers.     

Microsoft last week merged Skip Ahead and Fast Ring testers so that now both groups will be testing 20H1 builds, rather than 19H2 as was expected. Microsoft plans to release 19H2 bits to insiders this spring.  

Meanwhile, it's moved the Windows 10 May 2019 Update over to the Release Preview test ring for a final round of testing before releasing it to the general public. 

It's possible Windows 10 19H2 will be a minor update. The 19H2 release will have 30 months support for Enterprise and Education releases versus 18 months for the H1 releases. The change in pace could help convince enterprises running Windows 7 to upgrade to Windows 10 before the end of Windows 7 support on January 14, 2020. 

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