As the title says any time I use Alt Tab the game will freeze and the only thing I can do is close it using the task manager.
It does not matter if I run in Fullscreen, windowed or borderless mode, it happens no matter what.
Some research I have done on the issue seems to indicate that this has been a problem since beta, still is a problem and that is generally "not advised" to Alt tab.

To advise players not to use alt tab suggest to me that the game is designed in such a way that doing it will cause problems which in my opinion is poor design, and no other game I have played have displayed issues like this.
I also have this problem where my games will alt tab or loose window focus in windowed/borderless mode(I have yet to determine the cause of this and fix it) which causes the game to freeze/hang on me, so I have to close it using the task manager.

This becomes extremely frustrating since the alt tab or loss of window focus happens quite frequently making it impossible for me to get anything done since all mission progress will be lost upon restart forcing me to start the missions over again.
I was trying to play some co-op with a friend yesterday and had this happen to me so many times I lost count, and made it difficult and frustrating at best to play.