When I put a campaign in queue, and process it, I see the message that the number of list members in that list have failed and will retry.
When I stop processing and look at the campaign in the campaign list, I see that it has an inflated number of number of messages sent. The number sent being over 10,000 more than the total list members.
The version I am using is 3.3.9 (unable to upgrade), and I am looking for advice on how to trouble shoot the issue.