APNS when not in app causes sever lag/crash

I am sending a push notification from my node-js server. I set the badge count to 1. It works fine when my app is in the foreground, didRegisterForRemoteNotificationsWithDeviceToken gets called and the app does what I want. What I want is a UI action, basically something that the user has to do. However, if I lock my phone and then do this notification, it doesn't show the UI. I know it has called the notification because it says failed, and it lags the app/phone severely. Does anyone know how I can get this UI element to pop up and not lag the phone when the push notification happens? Thanks