Steps to reproduce:
1. Create a clean installation of eZ Platform.
2. Create two Landing Pages "test1" and "test2".
3. Set the tree_root as follows:

ezpublish:
    system:
        site:
            content:
                tree_root:
                    location_id: <test1 location id>

4. Remove cache manually rm -rf var/cache/*.
5. Visit the BO and try to edit "test2".

Result:
You will be presented with the following error:

Parameter "siteAccessName" for route "page_builder_content_preview" must match "[^/]++" ("" given) to generate a corresponding URL.

Expected result:
Landing Page "test2" is editable.

Note:
Ibexa DXP v3 is not affected.