I imported the furniture demo, and went to customizer to add some additional css to modify stuff a bit. And I wanted to see what other options there are in the theme. So I clicked on the Header settings and on layout and the whole customizer panels were offset by 50% and are not visible.
As you can see from the image, something ain’t right 😀
From what I’ve inspected redux adds this css
media only screen and (min-width: 1125px)
Which affects how the customizer behaves.
You should notify the developers at redux to fix this, or overwrite it in your own theme…