Post pages started displaying with footer in middle of page

I am taking over the maintenance of a website, and know nothing about this theme. I hope this is a simple fix!

The most recent two posts (and when I "add new" posts), are displayed with the footer in the middle of the page, and a part of the social icon widget (I think) through the header, making the header impossible to read. I assume this is some kind of CSS issue, but not sure why it only happens in the recent and new posts and not the others!

Any ideas where to look for the issue, or how to fix it?

Thanks!