1. Create two languages - eng-DE (English) and ger-DE (German).
2. Create the following config in ezplatform.yaml:

           list: [ger, en]
           groups:
               group:
                   - ger
                   - en
           default_siteaccess: ger
   

           ger:
               languages: [ger-DE]
           en:
               languages: [eng-DE]
           group: #group consists of ger and en
               content:
                   tree_root:
                       location_id: 42 #ID of default Ibexa Platform folder
   

               page_builder:
                   siteaccess_list:
                       - ger
                       - en
   

3. Set alwaysAvailableFlag in LandingPage Content Type to false.
4. Create new Landing Page under Ibexa Platform folder in German language.
5. Add Text block and publish it.
6. Translate the newly created content into English language.
7. Edit the Text block and submit it.

Result:
Cannot update blocks preview exception being thrown.

Expected result:
There shouldn't be any exception.

Note:

1. The block updated data saves successfully, this is just a matter of preview.
2. Issue doesn't occur on v2.5.