I have a sticky absolutely positioned header menu that works very well until viewed on mobile XS (portrait) breakpoint. Mobile SM (landscape) works fine.
When viewed in portrait on an iPhone the page will not scroll without trying many times. I have not tried on android but on the iPhone in portrait mode the scroll is buggy.
However, I have a snapshot from last week below that works.
I can not tell what has changed within the header menu and have tried to copy the working dev settings to the staging site. Perhaps the problem lies elsewhere.
Would appreciate any suggestions about where else to look for a fix.