Here's my issue:
I've added two date fields to my event content type, each are allowed to have repeating dates, but I'm seeing all the repeating dates from the first date field in the date selected for the second date field. So for example if my field_date_first has a date set as well as a repeating date and my field_date_second has just a date set, in the calendar when the field_date_second renders it renders once for each of the field_date_first dates.
In the calendar view I've configured the contextual filter to include both date fields and am using the "OR" method. I don't believe there is a misconfiguration in my view but that the calendar, when building items to display, needs some additional filtering. I've attached a patch that restricts multiple duplicate items from the $items array. The unique key for an item is built from the item ID, item start date, and the item start time. If this "key" has been used before it's not added to the $items array. I'm not sure if it's the best solution, but it fixes the issue I'm having. The patch was made against the 7.x-3.4 version hence why 3.4 was selected for this issue rather than 3.x.