User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:70.0) Gecko/20100101 Firefox/70.0
Firefox for Android
Steps to reproduce:
There are 3 pages, including one I develop, that suffer from this glitchy behavior:
Visit any of them on Firefox for Android or another OS with touch screen functionality. Make sure you scroll past the background image. It won't be reproducible on top of the background image, only on content below it. Then start scrolling up and down without taking the finger off the screen.
Due to how the address bar on Firefox disrupts the viewport height, you will see the background image resize abruptly, the content below will "jump" out of its place and the scrolling position will be locked. You will be prevented from scrolling unless you take your finger off the screen and scroll again.
The scrolling shouldn't lock in place. The contents of the page shouldn't be disrupted by the Firefox UI.
On Google Chrome, the address bar doesn't disrupt the viewport height, so none of these glitches are reproducible there.
There is only one website (which contains the same features) where I cannot reproduce this, at all: