Any NPC follower wearing a helmet will equip and de-equip it as they move, leaving a new helmet behind on the ground. Whilst it’s fairly amusing to imagine a survivor continuously vomiting riot helmets as they run it breaks the game a bit.
I can provide screenshots if needed.
Please do provide screenshots. Just for the hilarity, hehe.
http://imgur.com/4ZBHgKZ
Here’s the one I took when it first happened. Note the helmets all over the road, haha.
I see it: it looks like NPC code doesn’t account for items that aren’t in inventory or wielded when wielding a new item.