Can't install El Capitan update 10.11.3 because can't restart normally I've got the typical problem that OSX can't shutdown/restart normally. I'm on El Capitan but it happened in the past with Mavericks etc. Don't know why they can't fix this...

Anyway, now I want to install El Capitan update 10.11.3, the final step is it wants to restart the system.

I click the 'restart' button but the restart fails.

I can hard boot by holding down the power button... but then the update doesn't finish its install - it still says I need to restart if I go into App Store.

Restart or shutdown from the Apple menu don't work.

I tried a shutdown -r now from Terminal... this successfully restarts but the update still 'needs restart' when I go back in after booting.

MacBook Air (13-inch, Mid 2012)
El Capitan 10.11.2
I was able to complete the update by:


hard shutdown (hold down power button)
boot into safe mode (hold down shift when powering on)
open App Store and click Restart for the uncompleted update


was then able to restart successfully from safe mode, completing the update