Deceptor,
I changed nginx back to ip_hash on the upstream app nodes and re-tested vbO. It now shows successful on the tests. I had been using ip_hash most of the time (forces same user to same app server) but had disabled it when I was doing some of my admin testing and editing because I wanted to see both nodes live for myself to make sure there were no issues. I had forgotten to re-enable it. So, mystery solved, and I'm happy to accept responsibility for it being my config
I knew if we worked together we could solve it.
Mike
I changed nginx back to ip_hash on the upstream app nodes and re-tested vbO. It now shows successful on the tests. I had been using ip_hash most of the time (forces same user to same app server) but had disabled it when I was doing some of my admin testing and editing because I wanted to see both nodes live for myself to make sure there were no issues. I had forgotten to re-enable it. So, mystery solved, and I'm happy to accept responsibility for it being my config

Mike