So yesterday we tried backing out RabbitMQ server to 3.8.5, as the errors seemed to start when we switched to 3.8.9(but other things did change as well, ELB->NLB, new K8S cluster) So I thought I would just change ONE thing at a time, The RabbitMQ version was the easiest as that is under my teams control.
It didn't really help the issue. But I think it at least helps me rule out RabbitMQ server as the issue. Nothing on any of our clients side changed. So I'm going to try work with the network folks more to try capture some data.
Just thought I would update what I have found so far.