It now has happened on two of my computers. Via Windows Update the AU has been downloaded but not installed. Both just installed the updates for 1511 but the AU still remains. A third computer did install the AU, the fourth is sitting idle so not sure what it will do when I turn it on.
I know I can install the AU manually but this seems like a messed up way to distribute it.
Maybe count yourself lucky you're not (yet!) in the situation of a failed AU upgrade with an unbootable PC, and no disk images...
Note the latest update to the AU - some 100's of Mbs- is stalling indefinitely during the download for many. Possibly sthg to look forward too... (fixes posted in related threads- which might be of help here).
Search for threads on KB3189866 incl. the News forum.
If KB3189866 stalls or doesn't install, you can manually download it from http://catalog.update.microsoft.com/v7/site/Search.aspx?q=KB3189866
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