Alarm Volume Decreased Over Time

When I first set up my Ring system a few months ago the initial tests of the Alarm showed it to be quite loud, however, I noticed it went off last weekend and discovered on my phone hours later that the alarm was ringing. I had set it to Away mode the night before, then in the morning my daughter opened the back door and set it off before I had a chance to change it to Home mode. It was literally "ringing" for hours before I noticed it on my phone and turned it off. What causes this and is it broken or is there a way to reset it?