Schedule block layouts don't work correctly

Steps:
1. Go to eZ Studio.
2. Create a new Landing Page.
3. Add a Schedule block.
4. Choose a template other than hero e.g. list.
5. Add a content item.
6. Add second content item.
Actual: Dialog is displayed to confirm push-out of first item.
Expected: Second item is added and displayed on the list.

Remarks: Occurs also for grid layout