This looks like following issue: https://issues.jboss.org/browse/JBPM-3722 that in fact I can reproduce. Could you please comment on following:
- what peristence.xml settings to you use - especially important hbm.ddl.auto
- have you tried to clean up db and start fresh?
- is there any other modification to the installed jbpm (using installer) then the CustomWorkItemsHandler.conf and putting handler on class path?
Anything else you could think of for your environment.
Cheers