How to handle stuck updates?
Try the combo updater instead - https://support.apple.com/kb/DL1970 for a direct download link which you run like any app.

You can always Google for "10.x.y combo update" &amp; it will be the top hit.
It will apply all updates since 10.x.0 without needing any intermediate updates &amp; is often used to fix odd update glitches.

Failing that, then try reinstalling the OS from Recovery.
This will not affect existing apps, docs etc - though of course, as with any operation like this having a current backup is always wise.