Root cause: If multiple connections are opened at the same time after an update, the ui-middleware will do multiple requests to get initial data. That went especially worse, when e2e-tests are launched against ui-middlewares with multiple clients connecting at the same time.
Soltion: Make sure, that a node already caches stuff without a response.

Root cause: configuration was only reloaded on those nodes, that did the version update. The other nodes might not notice that.
Solution: On propagated version changes, the nodes always check for config changes