I could not reproduce the issue. Version 2.8.4 will contain some extra checks. An error message either from the error log or the feedburner service is needed so as to know what causes the issue and if it's related to Add-Meta-Tags.
Does this problem happen always or periodically. In case it happens periodically, it most probably has to do with server connectivity issues due to overload. In case it happens always, then an error message is required.