Incorrect behavior when changing elements in the slider

[zavsievich]

I have an array of arrays. I'm rendering the child arrays as slider elements. When I change the state, I change the array that the slider renders. Instead of swapping elements, it renders new slides internally, bloating the DOM and duplicating navigation elements.
This behavior is reproduced if slider elements have a unique key. If you remove the key (react swears on this), the bug doesn't reproduce.

Representation:
https://codesandbox.io/s/dawn-paper-y8pld4?file=/src/App.js