Steps to reproduce:

1. Create multisite config as follows:

           site:
               languages: [eng-GB]
   
           site2:
               languages: [eng-GB]
               content:
                   tree_root:
                       location_id: 57
   

   where location_id: 57 is ID of newly created folder (name it "test") under Welcome to eZ Platform Enterprise Edition Content.

2. Create another folder inside the newly created folder (name it "issues").
3. Go the folder created in the previous step to frontend using site2 SA (http://localhost/site2/test/issues).
4. Folder is visible - that's fine.
5. Create URL Alias for this folder named "error" - use Place at the site root option.
6. Go to the following URL: http://localhost/site2/error.

Result:
404 exception:

No route found for "GET /site2/error"

Expected result:
No exception, you should see proper folder info rendered.