For the error, did it stop Tableau Server from coming up altogether? Also, is this a Production or non-Production environment?
In some ways could almost see this in that when you setup a Backup Primary, I'd think you'd want all the workers down as well as the Primary itself. After you go through the steps of setting up a Backup Primary, the workers can then accept commands from either the Primary or the Backup Primary. Some folks get a bit confused and think you can have both running at the same time but you really can't. In the near future, the Backup Primary will be going away. It's been mentioned in another thread but for the Linux version of Tableau Server you can move Licensing to different nodes within the cluster so there's not really a designated Backup Primary. The goal is to bring this over to the Windows version in a future version.
If you restart Tableau Server do you get the same error message?