The Cloudbees Folders Plugin (https://wiki.jenkins-ci.org/display/JENKINS/CloudBees+Folders+Plugin) allows to organise jobs in a directory tree.
Workspaces are also organised with the same directory tree.
This plugin doesn't work if the job is in a folder
To reproduce it :

• Create 2 slaves with the same label
• Within a folder create a job attached to the label which creates are file in the workspace. This just is configured to use the wsclean plugin (before or after)
• Stop one slave and execute the job
• Restart the slave, stop the other one and execute the job
• Restart the slave (you have a workspace in each slave) and launch the job
• You always have the files in the 2 slaves while only one (the one with the latest execution) should have it