I normally swap between 2hd sword and bow during combat and frequently the animation gets screwed up and my 2hd sword just disappears. I can still attack, the animations play out but it looks super stupid without an actual WEAPON in the animation. When this happens my bow usually ends up laying on the GROUND ON MY FEET instead of being strapped to my back.
It doesn't technically affect combat whatsoever because I'm still hitting with the weapon, it's just an animation glitch. The only way to fix it is to manually unequip my 2hd sword and then re-equip it.