Steps to reproduce:
Create a space with at least two versions (1.0, 2.0).
Create a page in version 1.0 only.
Select version 2.0 in Confluence.
Switch to the viewport view.
Select "Edit Page".
The edit mode is shown.
Click the "Close" button (don't save).
The display jumps to the Confluence view mode.
The Viewport Control takes up the entire browser screen.