We would need links to your read-only page to confirm.
My suspicion is that you are setting z-index values on buttons, or things within a container, and not on the container itself.
z-index is a little strange in that those values are ALWAYS relative to whatever container they are in. So, if you’ve got a navbar element z-index 0, even if you set a button within the navbar to z-index 9999, they will still get covered up by any other element on the page with a z-index of 1 or higher.
I hope that makes sense. Basically, check your button’s highest parent element and see what your z-index is there, and that is likely where you’ll find your problem.