Dynamically change checkboxes with Angularjs

I'm getting crazy with a simple checkbox.

This is it:

input(type='checkbox', ng-model='auto', ng-checked='auto', ng-change='save()')

So, as soon as I save it from the method in ng-change it save the auto value correctly but the app also listen to SSE (Server Sent Events) to update that value:

A simple example:

$scope.$watch(Auto.getNewValue, function (newAutoValue) {
    if (newAutoValue !== null) {
        $scope.auto = newAutoValue;
    }
});

Even if from the $watch the value is false but previously I checked it the ckeckbox remain checked...

How should I uncheck that checkbox with AngularJS???