Body of five random posts disappeared (from front-end only)!

Since upgrading to 2.6.1, the body of five of my posts (seemingly random ones) has disappeared from the single-post front-end.

The excerpts display when reached through a category or tag link and those recent enough to be on the front page display the post before the ‘Read More’. But the single post displays only the title – none of the body at all.

Thankfully, all the text is still there is in the backend if you click on ‘Edit’. I’ve tried re-saving but it doesn’t fix the problem. I only stumbled upon this because I was checking an old post. Does anyone have any idea what’s going on?