The issue happens in case of concurrent requests to several Smart routers to register Kie servers for container. Some of Kie servers are missing in config file after the last synchronization is finished. The issue is caused by Smart routers overriding config file updated by other Smart router instances before the changes are fetched.

The issue can be partly reduced by setting smaller refresh intervals, however it doesn't eliminate the issue completely.
My suggestion is to load configuration file every time Smart router gets a request to register/unregister Kie server. This way the Smart router will always work with the most accurate configuration.