Exit app is not working some time

In Some times, Exit from app is not Working when click on back navigation. Blocks are provided below.

always switch screens correctly


There is no issue when closing a screen. Only problem when close application function

read this for better understanding why switching screens also affects closing the app
App Inventor Tutorials and Examples: Manager Screen | Pura Vida Apps
protip: therefore switch screens correctly to be able to close the app

How set it if we opens screen with a value?