Changing View Issues

Platform: Hololens

I have encountered an issue with Studio when trying to change a particular View in Studio. 

I have 5 Views (a, b, c, d, e) and in each I have enter the following code into the corresponding javascript file. 

// Change scene 
$scope.app.goa=function() {
twx.app.fn.navigate("a");
};

$scope.app.gob=function() {
twx.app.fn.navigate("b");
};

$scope.app.goc=function() {
twx.app.fn.navigate("c");
};

$scope.app.god=function() {
twx.app.fn.navigate("d");
};

$scope.app.goe=function() {
twx.app.fn.navigate("e");
};

I also have 5 Application Events (a, b, c, d, e) each with the corresponding function to load the correct scene e.g. 

app.goa();

When I run the preview these application events work for all but 2 Views. And after clicking the Application Event to load a broken scene this prevents any other buttons from working. 

I have also tried changing view without using javascript and relying on bindings but this leaves me with the same result. I have remove all other code form the .js file but still nothing. 

Can anybody think of what could be going on here?

Many thanks.