WP Update deleted code from pages

I’m not entirely sure which update did this, but we utilize a theme that allows for use of Font Awesome icons within the page/post content of our site.

Since the last update, every html tag I had defined in my site via the page/post content panels has been deleted.

The tags in question will appear like
<span class=”fa fa-cog fa-2x” style=”color: #11a4b7″></span>

What’s especially bizarre is that placing the tags back into the page/post content restores the page and the Font Awesome Icons start displaying again.

Anyone know why a tag like that would be deleted during an update? I’ve made no changes to the theme or other plugins. I’d turn off WP auto-update for WP if I knew how since I now get to correct over 50 pages of content.

Site is http://www.event1software.com.
Example page that had FA spans deleted is http://www.event1software.com/product/office-connector-suite/.

I’ve since replaced the icons on that page but need to know how to prevent something like this in the future.