The Calendar view is only showing all items for a particular day when we apply an assignee filter.
We have 6 stories assigned to the same day, 23rd October. Three are assigned to one person, the other three to a second person.
If we clear all assignee filters, we only see 4 items shown in the Jira Calendar View. See first image.

If we filter for the 2 people the tasks are assigned to, only then do we see all 6 items in the Jira Calendar View. See 2nd image.

Why is this?
Thanks
T.