Child components unmounting and remounting

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* Please replicate your issue with this [CodeSandBox](https://codesandbox.io/s/ppwkk5l6xx) and provide a link to it along with the issue description

The Slider component seems to unmount and the remount all its children. At least all the numbers appearing twice in the console indicates so. I have a component that does some fetch requests in the useEffect(()=>...,[]) part but because of the mentioned behavior my components are make API calls 2 times. I don't know if it is an expected behavior or not.

Sandbox Link: https://codesandbox.io/s/react-slick-playground-forked-oqbhv