When moving from Content Structure to Page you also "inherit" the last visited in Content Structure.
This may seem like a good thing, but as it is implemented now it only works for the "site" siteaccess that has it root location as default. As soon as you click on your own siteaccess things goes bad.

steps to reproduce:

• install ezstudio with demo content
• assign tree_root of a siteaccess to "Another Landing Page"

          no:
              languages:
                  - nor-NO
                  - eng-GB
              content:
                tree_root:
                    location_id: 105
  

• Login on admin interface
• Using the Content Tab, navigate to "Another Landing Page"
• Select the Page Tab
• Select Siteaccess: no
  => You'll run into a "no route found" error