Templates not displaying correctly on Safari

There seems to be a bug with several of the templates using Safari (desktop and mobile). The first time the page is loaded sometimes the content box is abnormally small and stuck in the left corner of the screen. I ended up with using “Slide up” which didn’t produce any apparent issues, but I would rather use “Pop up” if I could make it work. Other browsers like Opera seem to handle it better.

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