This is a very common issue on Elementor, and it happens more frequently on menu navigation and social media icons. The reason for this is that Elementor is not detecting that the icon’s font is needed on the page, and it doesn’t load the needed files. That’s why the error occurs on some pages, but not on others from the same site. The pages where this is working may be using an Icon widget.

The solution for this is very simple: On WP Admin, go to Elementor > Settings > Advanced and set to “Yes” the option “Load Font Awesome 4 Support”.