We have several jobs that make ui tests that need xvnc. Baddly sometimes xvnc is not able to start due to unavailable display.
org.eclipse.swt.SWTError: No more handles [gtk_init_check() failed]
When we edit hudson.plugins.xvnc.Xvnc.xml and try to change maxDisplayNumber it is not taken into account, each time the file seems to be rewrite.
Perhaps it is not a bug but a miss understanding on how xvnc plugin works.