Thank you Justin.
I gave up on it in production but re-created it in a testing environment: http://go.jewcer.com/test1/
If you go to the page on a desktop browser, the header is showing great (and sticky to the top). The actual header is at go.jewcer.com/header
However, if you go to the page on an iphone, the header is blank. When you go on an Android device, the header is showing.
If you disable the “sticky header” script, the header is showing again…
I have to say though, this issue was a small part of the reason I gave up on building the minisite like this. The bigger reason was that this is a workaround to the fact unbounce does not allow to share sections between pages which means that if someone views the page, I get “charged” multiple views (as part of my pre-paid package) which I think its somewhat unfair.