After upgrading from Jira Plugin 3.0.2 to 3.0.3, the following error is presented when trying to increment versions through Jenkins.

FATAL: Unable to add version 1.6 (170) to JIRA project XXX
java.lang.IllegalArgumentException
at java.util.concurrent.ThreadPoolExecutor.<init>(ThreadPoolExecutor.java:1307)
at java.util.concurrent.ThreadPoolExecutor.<init>(ThreadPoolExecutor.java:1230)
at java.util.concurrent.Executors.newFixedThreadPool(Executors.java:151)
at hudson.plugins.jira.JiraSite.createSession(JiraSite.java:457)
at hudson.plugins.jira.JiraSite.getSession(JiraSite.java:426)
at hudson.plugins.jira.JiraSite.getVersions(JiraSite.java:815)
at hudson.plugins.jira.VersionCreator.perform(VersionCreator.java:39)
at hudson.plugins.jira.JiraVersionCreator.perform(JiraVersionCreator.java:58)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:45)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:690)
at hudson.model.Build$BuildExecution.post2(Build.java:186)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:635)
at hudson.model.Run.execute(Run.java:1835)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:97)
at hudson.model.Executor.run(Executor.java:429)

Rolling back to to 3.0.2 rectifies the issue.