Page builder by SiteOrigin: weird gallery behavior

Hi everyone.

If you click on the page you get to the gallery (on the left). That looks ok. But no matter which image you click: down below there is only an option for ‘previous’. Click that and there’s an error; can’t find page…

What should I do to get this gallery up and running?

Hope someone knows!

The page I need help with: [log in to see the link]