Issue with adding duplicated content item in Schedule block.

Steps:
1. Create a new Landing Page.
2. Add a Schedule block.
3. Choose template ‘Studio Demo schedule list’.
4. Add content item ‘Valencia, Spain’ (Home/Places & Tastes/Places).
5. Add content item ‘Kochin, India’.
6. Add content item ‘Anchorage, Alaska’.
7. Add content item ‘Valencia, Spain’ again. [screen 1]
Issue: Valencia item is displayed twice, counter shows 3/4 items present.
8. Wait ca. 20 seconds.
Issue: One of the duplicated items disappears from view. [screen 2]
9. Add content item ‘Brooklyn, New York’.
Issue: Push-out confirmation is displayed, Schedule block displays 3 items but acts as if it were full. [screen 3]
10. Confirm. [screen 4]