Infinite Scroll stuck in 'placeholder' state if monitor is unable to scroll it into viewport (eg. Portrait-orientated monitors)

[NadyaNayme]

The first 15 items load and the next 3 are placeholders that trigger a load when they are scrolled into the viewport. On sufficiently tall enough monitors they are already visible in the viewport and so never load in. In order to trigger them into a loading state - the window must be resized such that the placeholders can be scrolled into the viewport which will trigger loading as normal.