Unable to Delete/ Unjunk mail from junk box and getting a warning: "unable to update junk store database".
rebuildsearchdb After this process, give it 10-15 mins. (During this time you will see a warning message on the junk box page saying "processing backlog emails <>% completed).
Check the webUI after 20-25 mins and you should be able to see the junk store database repopulated on the web page with all the emails.
Try to delete or unjunk the email now and it would allow you to delete or unjunk the emails.