Mission Control freezes. Restarting Dock doesn't help
The solution/workaround so far. 
Thanks to Shaded, who posted a comment with this workaround.

TL;DR

To unfreeze Mission Control without restarting MacBook


Disconnect external monitor
Close MacBook and let it sleep (optionally: Click "Apple" menu -> Sleep)
Open MacBook - now everything work again (monitor can be connected as well)


Details

It seems, that the problem is caused by some configuration issues when MacBook works with an external monitor.
After disconnecting the monitor, a display driver(?) is being reset(?), Mission Control doesn't freeze anymore, and monitor can be connected again.

Important note: The MacBook should go to standby mode (sleep) after disconnecting monitor. There is a 'Sleep' item in the Mac system menu. I didn't test if it works. I have just closed a lid and went to drink a coffee.

Another note: At the moment of freezing - CPU load is 100%. MacBook is getting hot and turns cooling fans at maximum speed.