Bug with missing or replaced elements at the front-end

Hello. I have a weird problem building some sites. In rare cases (1 time out of 10) elements or symbols (texts) are replaced automatically by others. It is not linked to a specific module, but sometimes appears in multiple sections of the site, and sometimes only in one section (as in the photo with the arrows replaced by the digits 4 & 5). The original elements are usually of the theme itself and directly used by the templates themselves, and no icons are added from other sites / themes. I am adding some pictures and links to one of the sites where the problem occurs. It's not in the cache, because a similar bug comes out to different browsers, despite clearing the cache. It appears completely at random to different users.
PS: The problem is not noticed in the tests performed on several mobile devices.
Website link: https://thinkeast.eu/ or subpage: https://thinkeast.eu/legaltrek/
Photos:
https://ibb.co/m0xpVz3
https://ibb.co/HT5WdCD
https://ibb.co/7NRS2FM
https://ibb.co/N9s57Yt