No, this is not it at all.
There is no peeking or movement involved when it occurs.
For example, you will be taking cover against the wall there, and shooting parallel to the wall. Without moving the mouse in any way that makes you look anywhere other than parallel to the wall, the gun will drop. Typically for me it occurs when I am tracking someone who runs past me. So if I am at that wall, taking cover against it in the middle (not at the edge) and an enemy runs past the reddish iron stuff infront of me, towards the yellow machinery to the right. I will open fire on him as he is running past the reddish stack and passes in front of me (so I am shooting parallel with the wall, and I'm positioned in the middle of the wall, not near the edge/corner), the gun will stop shooting and drop before raising again an instant later and resuming fire. This is usually enough time for the guy I just shot to turn, get a fix on me, and cut me down. If there is any movement of the mouse at all, it would be to track the guy as he runs towards the yellow machinery.
Now, if I were to stop taking cover against the wall while firing on him, it doesn't seem to happen. But I can't say for certain if that is the cause of it or not because it does not happen frequently. It happens just infrequently enough to be incredibly frustrating.
edit: or maybe that is what's happening to you in the video there but the smg has such high handling it's coming up quickly enough. If that is the case, with an AR it takes about a 1/2 second for the gun to re-set in the ready position. But when it happens to me, it is not because I am looking around a corner at all. I will be parallel with the cover the entire time and it will drop.








