No alarm sound after software updates

Every time my phone software auto updates during the night, the volume level or sound settings stop working. They return to normal after the phone is restarted but this is not helpful since I use the phone as an alarm clock. I was an hour late to work because the volume quit working during the night so I slept through the alarm. The alarm app was sending visual notifications as though the alarm was ringing, but no sound was emitted and the volume control buttons were frozen on the silent setting. The ringer switch was in the on position. I am not even sure that a software update happened this time. My phone has been very buggy since the last update. (I am one of the people with the 30% battery issue that allegedly does not affect iphone 6.) I am not going to try 10.2 until it tests better.