If you un-sheath a shield with a backpack skin toggled on, the back item will appear on your shield and not on your back for a small brief frame of time and then it magically teleports on your back correctly.
It’s such an eye sore if you’re a shield user and have a backpack skin on.
EDIT: Here is a screenshot from 9 months ago (lol) when I previously posted a bug report about it here on the forums.