Hi,
We tested your website with your custom code disabled (screenshot https://monosnap.com/file/Mohk5yKfWyOZnJlPOzskm0nCEMlWYY), which modifies the banner header’s z-index: 999, and observed that it works correctly (screenshot https://monosnap.com/file/OXF0E7010AW1PKA6aQHMxplnP7rkft) with the default z-index: -1.
Please note that changing the z-index to another value may cause issues that cannot be resolved otherwise.
If you are still experiencing the issue, please provide more details about the conditions under which it occurs, including screenshots or a video demonstrating the problem.
Kind Regards