I was reading another conversation regarding this same issue with Mission Control, and someone offered a solution that fixed this problem on my computer: Re: Mission control has stopped animating suddenly

It works again!

Yes, here is how you do it.

sudo defaults write com.apple.mail DisableSendAnimations -bool true

sudo defaults write com.apple.mail DisableReplyAnimations -bool true

I agree that all this idiotic Apple obsession with animating everything is cancer.  I just want to see what I asked for as fast as possible.  These animations are useless, distracting and make the Mac look like a cutesy toy rather than a real computer.  Apple's UI team is turning the Mac into the toy that Windows users said it was.

It's shameful.

I try to turn off every animation I can everywhere.  I just want a FAST UI without glaring white and hideous painful blue colors.

Give me back the UI from Snow Leopard without all this animated garbage.

Good luck.

Hello,

After much investigation, it turns out the GPU is running out of vRAM when the animation stalls occur. Put simply, it's being caused by the amount of pixels the GPU needs to animate. With the Retina display, a full screen window is 14 million pixels alone - combine this with lots of other large windows and it can overwhelm the capacity of the GPU. Therefore, I have found maximising windows has a significant effect on how frequently animation stalls occur - if I have lots of applications open but keep their windows unmaximised, animation stalls may not occur at all.

I did submit a complaint about this to Apple, and to my surprise an engineer had contacted me shortly afterwards asking me to forward over some sysdiagnose logs and a video recording of the problem so that they could investigate. After waiting several months, the engineer told me they see some use cases that can benefit from further optimisation, but confirmed the problem is ultimately caused by the system running out of vRAM.

I don't know about you but I am certainly wondering why Apple decided to use a GPU that could easily be overwhelmed by the Retina display, but at least this issue comes to some kind of close and I am reassured knowing it is not an underlying hardware problem.

I should also mention I recently went to my local Apple Authorised Service Provider as I had a separate issue with my iMac which required hardware service. When I went to collect my machine, I  tested an iMac they had on display as they also happen to be an Apple Authorised Reseller and I noticed the same animation stalls under the same conditions on the machine I tested.