If you have "UI closure when hit" disabled, your inventory will not close like normal, which is intended.

However, if you have an item in your hand, while being hit, it can nullify your current action - Such as tossing out loot, or moving slots.

You'd have to try doing it a few times, for the off-chance that you're not hit inbetween dragging nor tossing, but if you're hit the interaction fails.

For PVE, this is a hindrance when mass collecting loot, and needs looked at - Thanks c: