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I have this same issue.
If you do not select any items to filter, you can successfully see all items in the calendar.
If you select just 1 item to filter, you cannot see any items in the calendar.
If you select more then 1 item to filter, you can successfully see the amount of items that are filtered (like in your example above with 3 items filtered).
But why can we not see anything when 1 item is selected for dynamic filtering? That is probably the most common use case?