My apologies for the delay. I thought I had responded to your ticket already, it seems I did not.
I am currently looking into the reason for this issue for you.
It does not do it on the demo site and on our dev site.
It may be due to the fact you did not add any widgets in the footer.
From what I read about Jetpack’s infinite scroll feature it loads the next bunch of posts once you’ve scrolled down to 50% of the screen (or the posts currently viewable on the screen).
If you disable ALL the plugins except the ones required with the theme and the problem is still present, then it must be something with Jetpack or the configuration.
We are currently looking into it for you.