A customer has installed the logging subsystem as per this doc; however, although the pods all start and the elasticsearch cluster is green, they are not able to connect to ES from kibana.

We have seen many errors in the kibana-proxy container logs:

http: proxy error: context canceled

Environment: OSD 4.10.21
OpenShift Elasticsearch Operator version: 5.4.3
Red Hat OpenShift Logging : 5.4.3 

We uninstalled it and installed OCL 5.3 to check if it was version specific but got the same error.
We also increased the resource limits for the ES instances, but it didn't help.