Unable to default DFF at job requisition level

Summary:

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We have two descriptive felxfields "Budgeted Vacancies" at Job level and "Available Vacancies" at Job Requisition level 

The requirement at hand is to default "Available Vacancies" in Job Requisition with the value of "Budgeted Vacancies" when the respective job is selected. 

We have used Autocomplete with Object Defaulting Rule Type. But the value is not being defaulted. 

However, when we tried to retrieve the value of Budgeted Vacancies for the respective job entered in Job Requisition with Object Validation Rule Type, we were able to enforce the validation and value at Budgeted Vacancies (Job level DFF) is retrieved in Job Requisition. But the issue is we are unable to trigger the defaulting event using Object Defaulting Rule Type.