Hi there!
I had a look at your site and noticed you have quite a lot of plugins installed and one of them is Related Posts By Taxonomy. Since it also displays related posts, it may be overwriting the Jetpack module. try to disable it temporarily and see if that helps.
If the issue persists even after disabling it, it would be good to rule out other plugin conflicts. For that, deactivate all of your plugins. If the issue disappears then reactivate one plugin at a time. Refresh your page each time you reactivate a plugin to see what causes the issue to return.
Let me know how it went.
