parse error processing this item failed because of an unknown error when trying to parse its contents

There is parse error found in the Crawl log of a SharePoint 2013 environment. Processing this item failed because of an unknown error when trying to parsing its contents. (Error parsing document,Sandbox worker pool is closed,SearchID)

1. In order to fix this you can try to perform the following action plan:
2. Open "Local Policies”
3. Click on “User rights assignment”
   

   adjust memory quotes

4. Make sure that the search service account has the following rights:"Replace a process level token”.
   

   replace process level token

5. "Adjust memory quotas for a process"
   

   adjust memory quota

6. "Impersonate a client after authentication"
   

   impersonate client

7. Please make sure that the policies don't get changed afterwards.
8. Run a clear configuration cache
9. Start a full crawl and the errors should be gone.