With the Emotional Jenkins enabled in the post build step, when the job is allowed to run concurrently, builds frequently get stuck at "Emotional Jenkins is waiting for a checkpoint on ...<reference to a previous build that is still running>"
For example, if my job's name is "myJob" and I run build #314 and #315 concurrently. If #315 completes all the build steps before #314, the build #315 would have this message in the console log:
Emotional Jenkins is waiting for a checkpoint on myJob - 314
The issue is likely related to https://issues.jenkins-ci.org/browse/JENKINS-9913 and similar issues have been fixed https://issues.jenkins-ci.org/browse/JENKINS-10234
This line in EmotionalJenkinsPublisher.java may need to be changed.