Clock vibration setting: makes no difference, problem still occurs.
Plugged in and charging: makes no difference, problem still occurs.
Restarting phone: resolves problem temporarily.
Alarm sounded this morning as expected, after restart (not reset). Problem appears to develop over time. Suggests unresolved conflict or leak somewhere.
Observation:
I notice that SMS notifications do not suffer the same issue. The sleeping phone will always beep and show a light for incoming SMS even when it ignores the alarm. Same goes for incoming phone calls. Only the alarm clock fails to wake the phone.
UPDATE (Nexus 4, OTA 13 as daily driver)
After some testing, I can confirm:
Clock vibration setting: makes no difference, problem still occurs.
Plugged in and charging: makes no difference, problem still occurs.
Restarting phone: resolves problem temporarily.
Alarm sounded this morning as expected, after restart (not reset). Problem appears to develop over time. Suggests unresolved conflict or leak somewhere.
Observation:
I notice that SMS notifications do not suffer the same issue. The sleeping phone will always beep and show a light for incoming SMS even when it ignores the alarm. Same goes for incoming phone calls. Only the alarm clock fails to wake the phone.