On reproducing the use case, you could do an export and re-import into a test cluster. How is ratel and alpha accessed? If using port-forward to a particular pod, are all the pods getting same frequency of empty results? Sometimes, when port-forward errors may occur, and you have to terminate tunnel and reconnect.
The Java client is experiencing similar behavior in similar frequency? Is the Java client running as a pod within the cluster, or outside the cluster?
What Kubernetes implementation, version are you using? Are you using the default scheduler or another scheduler (noticed the spotinst in the nodeSelector)? Were any underlying nodes affected swapped during testing?