I’ve seen this on a live site and I was able to reproduce the issue in a clean MAMP environment with TEC 126.96.36.199 and TECPro 4.4.31.
Steps to repro the issue:
Create an event. Create a ONCE recurrence on a different day. Create another ONCE recurrence on another day. Create another ONCE recurrence on another day and publish the event. You should have 4 events, but it shows 5.
The first date, not the recurring dates is duplicated. You will see two events in the back-end on the same date/time and they are tied to the same post id/event series. The recurrences are fine (no dupes).
The issue goes away after rolling back a version.
Here’s two other customers reporting the same issue.