Any vehicle I enter with anyone else, everyone appears to be dead even though they aren't. Up-voted.

Try moving the weapon to the ground then equip it.

I think a rifle butt would be the best option, something like America's Army 3's melee.

I could see this being useful. Say you want to lean around a corner and switching left handed would be much safer as to expose less of your body. Maybe your character could have be right handed or left handed in the profile maker, and switching hands could impact your accuracy negatively at the cost of a safer firing position.

This happens even if I do not already have a primary weapon and I'm not moving anything else, only trying to take a weapon. And it's not always weapons, sometimes items like binoculars or weapon attachments too.

This same instance happened to me on low settings.

I've had this happen when I put my weapon down too. Once I got out of it by pressing V and another time I got out of it by smashing my keyboard.