System is unable to identify a grade change which should increase the annual leave accrual

Summary:

We have a requirement for Annual Leave accrual based on grade, ie Grade A-D accrues 25 Days, Grade E-H accrues 30 days. Our expression works as expected to perform this but, if there is a grade change mid year the system does not prorate the accrual, the change is applied for the whole year.

I have followed the 'Create Event Processing Rules to Reprocess Absences' as per the 24B guidance, albeit just for work schedule changes

I have attached the event to the Additional Details tab in the Annual Leave plan

The expectation is that during the period in receipt of Grade A-D the appropriate number of days are accrued, thereafter accrue number of days