Steps:

1. Go to Content structure.
2. Select site from siteaccess dropdown.
3. Hover cursor over element in content tree, e.g. Article -> Preview is displayed
4. Hover cursor over element outside content tree.
5. Hover cursor over element in content tree form 3.

Result: Preview is not displayed. User must hover cursor over other element in content tree to see preview See https://recordit.co/6Kj0wrSoI1