Purge obsolete workflow data 11.5.10.2

I have a couple of questions regarding purging workflow tables.   I noticed that the wf_items and wf_item_attribute_values tables are getting quite large.  I ran the concurrent program "purge obsolete workflow data" to no avail.  Further research indicates that in order for this program to select records for purging, the wf_items.end_date must have a value.  Well, most of our rows contain NULL for the end_date.  This is caused by error "ERROR in Workflow HRSSA 3120: Activity HRSSA/nnnnn has no performer".

This happens when enrolling a person in a training class via the LM module.  .  It appears that the class enrollment function tries to find the username in the fnd_users table, and since we have not implemented HRSSA, it will not find them in the fnd_users table and cause it to throw this error.  This results in the wf_items.end_date being Null.   We have about 5,000 employees and only about 100 are set up to be HR users.  We do not wish to implement HRSSA.