I can’t reproduce the issue of both headers displaying at the same time. Would you mind editing the file
\framework\views\global\_meta.php from the theme and change this line
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="viewport" content="width=device-width, initial-scale=0.9, maximum-scale=0.9">
Then test it again, you could also change the values instead of 0.9. Please check this about templated editing through child theme https://theme.co/apex/forum/t/how-to-upload-xtheme-to-child-theme/43246/2. But in your case, it’s
_meta.php. Again, this is not a fix but just to find out if it behaves the same on different scales.