One ivy-build job can build multiple ivy modules that are located in one git repository:
If one of the modules is removed from resp. renamed in the repository, the ivy plugin continues to trigger builds. These builds fail with "FATAL: Unable to find build script at...", as the module does not exist any more (at this location).
Current workaround: delete the module directory under $JENKINS_HOME$/jobs/<jobname>/modules/<module directory> and restarting jenkins resp. "Reload Configuration from Disk"