This issue is not related to the plugin or WordPress but instead an issue with Google Calendar itself. It’s a known issue that Google is working on and it's affecting a lot of people.
Here's the latest reply from a Google reply on that thread:
Best answer - Alice PB&J (Google Employee)
Thanks for your posts to let us know you're having problems. Whether this is affecting a calendar on a Special Olympics website, or one used by members of the military, or by a church, or any of the other situations you're experiencing, we know this is important and frustrating for you. I want to reiterate that our team is working on a fix. As I posted previously, the resolution will likely take a few days, and we'll be sure to update you here once things are back to normal.
I've noted that some people reported having issues even in Agenda view, and I'll investigate those, but in the meantime, many people have found switching their embedded calendar view to Agenda view as a good workaround.
Thanks again for your patience and all the helpful information you guys have contributed!