Formulas and lookups do not not update if they were populated from a prior task step.  The way to get them to update again is to change the fields that feed into them.  Since your formula is referencing the Return_Date_1 field, a change to that field should trigger the formula to run again.

So you could instruct your reviewing team to edit that field.

If you'd rather do it automatically, and you are using the classic designer, you should be able to do it via Javascript.  Assuming your Return_Date_1 field has a CSS Class Name of returnDate, Javascript like this will probably work (it just triggers the change event when the form loads: 

$(document).ready(function() {

  //Trigger the change event of the returnDate field upon form load.
  //This helps ensure formulas are updated.
  $('.returnDate input').trigger('change');

});