Steps to reproduce:

1. Configure site accesses in ezplatform.yml as follows:

       siteaccess:
           list: [siteeng, sitefre, admin]
           groups:
               # WARNING: Do not remove or rename this group.
               # It's used to distinguish common siteaccesses from admin ones.
               # In case of multisite with multiple admin panels, remember to add any additional admin siteaccess to this group.
               admin_group: [admin]
           default_siteaccess: siteeng
           match:
               URIElement: 1
   

        admin_group:
            # System languages. Note that by default, content, content types, and other data are in eng-GB locale,
            # so removing eng-GB from this list may lead to errors or content not being shown, unless you change
            # all eng-GB data to other locales first.
            # For admin this needs to contain all languages you want to translate content to on the given repository.
            languages: [eng-GB, fre-FR]
            page_builder:
                siteaccess_list: [siteeng, sitefre]
            content_tree_module:
                contextual_tree_root_location_ids:
                    - 2 # Home (Content structure)
                    - 5 # Users
                    - 43 # Media
                    - 48 # Setup
                    - 55 # Forms
            subtree_paths:
                content: /1/2/
                media: /1/43/

        siteeng:
            languages: [eng-GB]
        sitefre:
            languages: [fre-FR]

1. Create French language of code fre-FR
2. Create LP Content object in language eng-GB
3. Create LP Content object in language fre-FR
4. Edit LP in French language created in previous step - resolved site access should be sitefre
5. Go back to ContentTree and edit LP created in eng-GB language
6. Observe site access info in page builder preview:

   Editing:
   http://localhost:8033/sitefre/english-lp
   in English (United Kingdom)
   

Result:
Site access in page builder preview which is set is sitefre.

Expected result:
Site access in page builder preview which should be set is siteeng.