Good evening Craig and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
We are sorry to hear about the 404 error messages you are receiving while using recurring events.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Can you try re-saving your permalinks to see if that helps (as well as emptying any caching plugin you might be using).
Hang in there!
Geoff B.