When using “Copy to an Event” when viewing the details of a calendar event, it isn’t copying the end minutes. I think it might be only copying the start time and setting to 1 hour duration which messes up the times in our case.
E.g. A calendar event is created and the time is set to 7:00pm - 8:30pm. Then, click Actions, Copy to Event, and the new event window has the event from 7:00pm - 8:00pm. I can replicate it again by creating a calendar event and the time is set to 7:15pm - 8:30pm. Then, click Actions, Copy to Event, and the new event window has the event from 7:15pm - 8:15pm.