No animation with MissionControl? Why? I don't have animation for Mission Control anymore. It seems that it has been like that for few days. I have updated Duet a few days ago, maybe that's related...
What happened? Is it possible that someone disable it? Or, is it a bug or the sign that the hardware is damaged?
OS: 10.11.5
Hardware: MacBook Pro (2,3 GHz Intel Core i7, 16 Go, Intel HD Graphics 4000 1536 Mo)

Edit
I've tried to do in the terminal
defaults write com.apple.dock expose-animation-duration -float 0.25

then press enter
killall Dock

then press enter
It works. But when I restart the computer, it does not work anymore.

I've tried installing Duet (third party software which I suspected to be responsible). It did not change anything.
Edit 2
I've tried uninstalling Duet (third party software which I suspected to be responsible). It did not change anything.
I too, have Duet installed and lost Mission Control animations on last update.

I believe it's some lazy "bug fixing" on Duet's team: Duet was running and I got logged out of my Mac

defaults delete com.apple.dock expose-animation-duration


then run Duet and then

defaults read com.apple.dock expose-animation-duration


It's again gets set to zero.

So my solution so far is deleting expose-animation-duration setting and removing Duet from autostart for a time being.