I'm not sure if this is app related or phone related. Using a selection of volume control apps (Volume Control for example) I have found that if I reduce the Ring volume to zero then the System (and hence Alarm) volume drops to zero also. This might explain some missed alarms I've been getting. As soon as the ring volume is greater than zero then the System volume returns to 100% and Alarm to it's previous setting. What's up with that ?