Back-Out Life Events Process unsuccessful

Our benefits staff is testing open enrollment and mistakenly processed the open enrollment life event for all staff instead of just the subgroup that was intended.  She attempted to run the Back-Out Life Events Process and it resulted in errors.  The log file shows some people as being successful and others as being unsuccessful, but it doesn't give any information as to why.  The whole process ended in error I think because there were too many errors in the batch.

The user was not sure what dates she should be using for the "occurred" dates, but put in the effective start date of the open enrollment.  When I looked at the life events for an employee where it failed, the "occurred" date was the date she entered in the back-out occurred date fields.