Hi,
I saw your other thread about translation and the URL.
In the meantime, thanks for that, Jan or Benno will get in touch.
Because of the z-index: I saw an inline segment, namely:
If I temporarily (intentionally) remove the z-index, it would look like this:
Try putting the above code (because it's inline style) in the custom.css. It (also) affects gantry.
This was the only way I could check since I'm not logged in there.
I hope it helps.
Kind regards
Christine