Been having this issue for a few months now and can't seem to get to the root cause. My ringer volume goes to the maximum occasionally for no reason. Sometimes it happens when I plug it into the charger for the night and set the volume to about halfway for the alarm to wake me up. The alarm volume waking me up is fine, but when I unplug it, turn it off of Do Not Disturb and get ready for the day, the next call or text I get is full blast. Other times, this has happened just randomly throughout the day. I have done resets but it doesn't seem to be fixing the issue.