Hi Maciej,
I actually dont have a valid test case for the issue as it is happening all out of random. The only information that we have is that the JBPM4_EXECUTION table doesn't have the required row for the execution of the particular job. The jbpm history table - JBPM4_HIST_ACTINST and the job table -JBPM4_JOB has all the valid entries.
Thanks
Abdul