Build 19042.906 and 19043.906 are available in RPC and Beta Channel

"it fails with error 0x800f081f if you update from 19043.899, but works fine if you skip the update to .899"

Have you try to uninstall older KB5000842 (released 15th of March) and go back to .867 before update to .906?

New CU's are available together with new Feature Experience Pack.

Releasing Windows 10 Build 19042.906 (20H2) to Release Preview Channel | Windows Insider Blog

The installer is broken. It stops at 20% & then it fails to install.

@michaelleepow90,

Yes, it fails with error 0x800f081f if you update from 19043.899, but works fine if you skip the update to .899 and update directly to .906, 

A fix is coming on the next 21H1 cumulative update.

I bypassed the problem by updating directly from 19043.867 to 19043.906.

Confirm exact issue with a Defender update last night. Couple reboots and it finally resolved itself and installed the definition update.

You could also try kick starting it by manually installing def update:

https://www.microsoft.com/en-us/wdsi/defenderupdates

1349 was the one getting the error, but the next one 1358 updated just fine from W.U.  :-)

B.T.W.

The MS Insider ISO 19043.867 still comes with the legacy MS Edge.

No big deal because the new MS Edge Chromium is the first thing they make you download after a clean install.  

I expect they will fix that on the final MCT ISO release.  :-)

Confirm exact issue with a Defender update last night. Couple reboots and it finally resolved itself and installed the definition update.

You could also try kick starting it by manually installing def update:

https://www.microsoft.com/en-us/wdsi/defenderupdates

Thanks Johnny, 

I did several restarts for over an hour and nothing changed, the same defender update downloaded and installed fine on current public build.

I now just checked for updates directly from defender and that did the trick, after posting an error message that the service stopped, it was too fast to clear the error message and I could not get the snip of it. :-(.

It is not showing in update history, because it was updated directly from defender. We'll see what happens on next update :-)

New CU's are available together with new Feature Experience Pack.

Releasing Windows 10 Build 19042.906 (20H2) to Release Preview Channel | Windows Insider Blog

The installer is broken. It stops at 20% & then it fails to install.