I now have Javscript errors for you :o) This cluster pops up for the offending page tab:
Blocked loading mixed active content “/wp-content/plugins/shiftnav-pro/assets/css/fontawesome/fonts/fontawesome-webfont.woff2?v=4.7.0”
Blocked loading mixed active content “/wp-content/plugins/ubermenu/assets/fontawesome/fonts/webfonts/fa-solid-900.woff2”
Blocked loading mixed active content “/wp-content/plugins/ubermenu/assets/fontawesome/fonts/webfonts/fa-regular-400.woff2”
Although they relate to Plugins that controls the menus for the site (on full screen, ubermenu is used to create megamenus and on smaller screens it switches to shiftnav-pro. Both plugins are created by the same author) it is their use of Font Awesome that causes the problem.