Cant uncheck programatically after manual check on a checkbox: Angular

Once checked from UI(clicking on checkbox), I am not able to uncheck the checkbox programatically.

In the sample app, click on the checkbox to check it. Now click on the 'Un Check' button. The property in the background changes to false, but the checkbox wont un-check.

Note: if not manually checked, both checking and unchecking works programatically.

Link to the code editor