Enabling the Xvfb plugin on matrix jobs starts a Xvfb server for the job itself and one for each configuration.
The Xvfb servers for the configurations are stoppd properly, but the Xvfb server for the job itself keeps running when the job finishes. This ends up in locked screens and a vast number of directories.
We experienced that on a master only instance as well as in master-slave mode.
Xvfb plugin version 1.0.2