Something to add on regarding “html body scrolling behind the overlay “ subpage , it doesn’t always happen but occasionally it “catches” on upon finger scroll touches ,and this makes the overlay subpage not responding (freezed).
Issue only in iOS mobile devices , something to do with WebKit browsers.
I have googled for this issue and it’s seems like a common problem.
Because the lost of momentum scrolling in the subpages (overlay), I tried to add this in custom CSS “-webkit-overflow-scrolling: touch; “. Momentum scrolling works now in subpages but not perfect as the sticky “close link” is bouncing with the momentum scrolling …
Now a new issue appeared after I added the custom code, HTML body is scrolling behind the overlay…
In CSS I see this is set to “overflow: hidden; “?
Definitely some issues between WebKit (scrolling), iOS browsers & how it behave with overlay pages.