The answer depends on the "payment period" window, which runs from due date to due date (not calendar month).  This is best illustrated by an example:

A member has a loan with a monthly payment due date of July 25. A payment is made on June 30, advancing the due date to August 25.  If another full payment is then made before July 25, the due date will not advance, because the loan is still within that same payment period window.  If a full payment is made after July 25 (even if it's still in July), the payment due date will advance to September 25. 

This process works for both Line of Credit Loans and Closed End Loans that have the single payment per period flag configured in the loan category (value = P).