Ionic notifications 'onNotification' triggered twice on incoming notification

For some reason this event triggers twice on an Android device on an incoming notification.
Any ideas why? Is this a known issue?

onNotification: function(notification) {
                // Handle new push notifications here:
                switch( notification.event )
                        case 'message':
                              // some code that is executed twice
                return true;

maybe you put the onNotification callback multiple times on the document?

No. I use it only once.
My server send only one notification but my device recieves two.
So wierd.