I'm not sure if this issue you are mentioning is related the Kibana that is not loading at all from one node, or that the Kibana Monitoring page is not loading correctly but Kibana itself loads properly.
Because the timeout is relative to an API for the monitoring but other API calls are returning 200 so seems to runs correctly.
If it's a Slack Monitoring issue, where you can't load the monitoring page, let me know and I can ping monitoring team directly