I created a simple HTML page that displays the problem. With Chrome desktop version is okay but trying on different mobile device and with different browsers it becomes obvious that there is a bug.
Scrolling down, in my example with Samsung S6 and Chrome, appear a white band on the bottom of the screen that disappears after less than one second.
I believe this problem is generated from the header of Chrome (or browser you use) that disappears when you scroll down.
I created an example JSFiddle and loaded the HTML page on my server.
On the web I did not find answers to my question, I hope someone is able to help me. Thank you all in advance.
Tests performed (and failed) with:
Samsung S6 and Chrome
Samsung S6 and Samsung Browser
IPhone 6S and Safari
LG G4 and Chrome
LG G4 and LG Browser