Menu and some other icons not showing when loading from smartphone

Hello,

When loading my Home page http://alfinlibre.net/home/ from the smartphone there are some icons not showing properly.

Menu icon, going up arrow, and several ones in the testimonials area. It’s weird because it works fine (at least the menu and going up ones) in other pages.

Please see screenshot attached as reference.

Can you help with this please?

Kind regards.