Eh, that's nothing, few friend of mine had issues where Android would sometimes not ring alerts. Why? Who knows, maybe some weird bug that manifested itself in some combination of system settings and phone firmware.
I have multiple devices so I usually set alert on home phone + work phone if it's something really important like a flight at 6 AM; but if I were to use an alarm clock everyday I'd probably buy the simplest one I can find for few bucks.
I stopped using Samsung's clock alarm for this reason. It's quite hard to figure out as a heavy sleeper whether actually only 1 of my 5 alarms went off or I was just sleeping through them.
One day I just stared at the clock app, not ringing, as my alarm time came and went. At least validated all those times I've doubted myself.
Downloaded AMDroid now. Much better, and much more customizable, and it turns out I never actually sleep through an alarm, they just never went off.
I also got really good at multiplying 2-digit numbers in a sleep-daze.
My Samsung and now Nokia have gaslit me into long-term self-doubt if I sleep through alarms. In one near miss, I noticed the volume was lowered without my intention.
I got bit by that twice and figured my old standard alarm clock would be good enough. Had it for 15 years and it has never missed a day.
In industry, the more reliable you need something to be, the more simple it has to be. Phones are too complicated to be a good alarm clock. Plus I don't have to blast out my eyeballs to see what time it is in the dark.
I have multiple devices so I usually set alert on home phone + work phone if it's something really important like a flight at 6 AM; but if I were to use an alarm clock everyday I'd probably buy the simplest one I can find for few bucks.