Position Field Modification Rule Not Firing Consistently

Summary:

We have created a Field Modification Rule on the Position and set the triggering field as Job. Expected behavior is that when selecting Request New Position, after entering the Job, if the rule logic is not met (Job DFF - which is a check box, is unchecked) then a warning should appear. In testing this rule on Request New Position, sometimes it triggers as expected and sometimes it does not.

The delivered rule, Default Probation Period based on Job Family of the Selected Job, was referenced when creating the logic. The desired behavior here is for a warning to appear. We do not want an error since we want users to be able to proceed with the transaction.