Hi @gina_masequesma,

As a Canvas admin for my institution, I see something like this perhaps once or twice per year.  I believe it's usually due to teachers editing the HTML or copy/pasting HTML from one site to another instead of using the menus build into the rich content editor to find and link to content.  Can you perhaps tell us how you usually create your content?  Do you ever copy/paste or go into HTML mode for things at all?

I know this isn't an answer but I see nobody else has responded for a couple days so trying to at least help narrow down possibilities here.

-Chris