2.11.0 unveiled a critical bug in the cluster config sync. Before you panic – upgrading the config master as documented before any other instance keeps you safe. The 2.11.1 release is for everyone upgrading their satellites/agents first. For those who cannot do a major upgrade on their masters, we also release 2.10.7 where we added an additional fix to prevent this behaviour.
The online documentation additionally covers troubleshooting topics for configuration problems with command endpoint agents and zone-in-zone synchronization.