Alarm doesnt sound if app in background?

Great concept for an app, but for the past 2 nights, the alarm hasnt gone off. Luckily, I set multiple alarms, so I was able to wake up. My watch told me that I had 16 notifications from the barcode alarm app, but alas, my phone (which was not on silent) didnt move or sound at all. Great concept, but buggy from my experience. I have the iPhone 6 with iOS 9.2

uhhlaurenyeah about Barcode Alarm Clock