I've observed several times that swapping items (have seen on chest & backpack items) that there is a visual duplication. I've not seen this result in actual item duplication.

At best, there is a lag between item changes where both are displayed but when it really bugs out it doesn't self-heal until you get out of inventory window and go back in.

The second video is much longer but shows both initial interactions at the start, and having another go towards the end and the UI really getting confused showing items without icons and just showing a green dot while trying to drag items.