Click left but goes all the way to the start

When using the `initialSlide` option, the first slide to be shown is the correct one. But once you click next or previous, it will move as if you were standing on slide 1. This started on `0.27.9`, `0.27.8` works fine

Test on: https://codesandbox.io/s/react-slick-playground-forked-n61d0?file=/index.js