I have the situation where Jenkins will not notice that the lock was released, so several jobs in the pipeline lock & release the lock, but at one point the release event seems not to be published, so the lock remains present.

It will also remain present throughout jenkins restarts, and there doesn't seem to be a way to administratively remove the lock.

This is the transscript of the build process: jenkins_arangodb_mesos_lockup.txt
I've attached the jenkinsfile, its also available through:
https://github.com/arangodb-helper/JenkinsScripts