Calender Events - why is the original author the only user able to edit or delete?

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Any other user gets an "Access denied" error when trying to edit the event. Even user 1, which has the highest level of privileges.

This is happening on: Drupal 8.9.14 opigno_lms-8.x-2.20 opigno_calendar 8.x-1.7 opigno_calendar_event 8.x-1.4