An intentional leak characteristic curve for the respiratory therapy system is determined based on a plurality of flow rate values and a corresponding plurality of pressure values for the plurality of flow rate values. An occurrence of an unintentional leak is determined based on the intentional leak characteristic curve. It is determined that a user interface issue with the respiratory therapy system exists based on the occurrence of the unintentional leak, wherein the user interface issue is one or more of an issue associated with a user position, a user interface tightness, a user interface age, and condition of a user interface seal associated with the respiratory therapy system.