You have a noisy controller.
Does it trigger if you're approaching a bit of cover then shoot -over- it?
P.S. If you need help making a video of you shooting at someone else, I'd be willing to give a hand.
Doing a little testing of my own: you should use machinima 'stage' level, since it has all weapons.
I was able to reproduce your video easily. Shooting at my feet, though, no problems whatsoever.
Shooting at an angle, either high or low also meant no problems. In the machinima level there are some broader pieces of cover. Shooting the
upper side of them doesn't cause the issue, it seems. Nor, strangely, does shooting the
upper corner.
I tossed up a canister onto a wall and shot at when I was way too close, firing at its lower-left corner, and all three times I blew myself up.
Again, in the stage mode there's a big block set into a wall. Approaching that, aiming way up, it seems to trigger it.
Also, I tested the sniper rifle and the FAL, and scopes seem to eliminate this issue. The GAU also seems to aim straight.