Maven projects with downstream maven projects push SSE to Blue Ocean but the event payloads contain URL's which 404. The downstream jobs are nested inside of the parent / triggering job, and these are converted to Blue Ocean style REST URL's but do not resolve.

This was evident on the Apache build server on 2017-12-07: https://builds.apache.org/blue/organizations/jenkins/pipelines

See attached HAR file for the 404'ing requests. An example of one of the URL's is:
https://builds.apache.org/blue/rest/organizations/jenkins/pipelines/Camel.trunk.notest/pipelines/org.apache.camel:camel-reactive-streams-starter/runs/3996/

Be advised this issue will be less evident once the below PR is merged, since it will reduce the number of background fetches made in response to SSE. Use commit 31f4fcc for best repro. https://github.com/jenkinsci/blueocean-plugin/pull/1581