Looking at the error messages, the failures are due to overlapping elements, and looking at the screenshots, it appears that the header bar is overlapping links that are trying to be clicked. In the attached screenshot, the step "I turn editing mode off" was attempted, but the bar was overlapping the button.
As I understand it, "Browser specific fixes" are in place to stop this happening, but they aren't applied to Firefox as they weren't required. Can anyone explain the issue I'm seeing?
I've tried both Firefox 38 and 45 ESR versions with the same result, running on RHEL7 64 bit.