Thanks for the link and what to look for.
I accessed the admin area of the site to investigate further. To fix, I had to disable the Open Graph - K2 plugin and re-order the JFBCSystem plugin to the top. I'm not sure where the conflict with the ordering of the system plugin is coming into play. You honestly have a huge amount of system plugins enabled, which I'd highly recommend going through to disable whatever you don't need. That will decrease the amount of conflicts you run into in the future and make a drastic improvement on your site loading time, which is a bit slow. Every system plugin loads on every page and does something, and that all adds up a bit.. even with 3 caching plugins enabled.
We'll have to investigate further to determine why the Open Graph - K2 plugin is causing issues with creating issues on the front-end. It's not something we've heard of before. If we can recreate the issue on our own dev systems, that'd be great. It may be a unique combination of extensions and plugins on your site that's problematic though as we've never heard of this before.
I hope that helps get you started for now, but if you need anything else immediately, just let us know.
Thanks,
Alex