Hi and welcome 🙂
Based on my experience with the data highlighter tool, there is the potential of a theme and/or plugin conflict based on what you’ve shared with me.
What is a good search query to run to see how Google is displaying the event rich snippets for this site?
I typically resort to doing a Google search along the lines of:
“site:http://your-site.com/event/single-event”
I see you have Yoast SEO plugin installed on your site and you have a Google Webmaster account. Between those two, you should be able to fully manage the SEO titles, descriptions, etc. Please let me know if this helps answer your question and have a great rest of your day!