Just got the Same issue with a Nokia 3
Some times instead of alarm or other notification sounds (unlock, lock, etc.) there is this loud siren sound.
send in to repair and they install android new. but after about 10 alarms (set it every minute to reproduce) there was this siren sound. I do a factory reset, now it takes about 100 alarms and siren sound.
now we send it in 2nd time with a video left on the phone. also said to care chat if theres no change i want a new phone. think this is a hardware fail.