Keyboard control for navigation slider

When running 2 sliders on the same page, where one of the sliders is in "asNavFor"-mode there is no keyboard access to the navigation slider.
I can't tab to the bottom slider and activate it via the keyboard. As far as I can tell all the items in the "navigation slider" has `tabindex="-1"` making them unreachable via keyboard.

Here is an example: https://codesandbox.io/s/react-slick-playground-forked-mc4c1