Here's the scenario. Sunday was Nov 7, 2021, I live in U.S. eastern time zone so time change happens. The watch time updates automatically, all is good. Set alarm to wake up at 5:05 Monday morning (once, vibration only). It works. Set time to wake up at 5:05 (not recurring, once, vibration only) for Tuesday morning and it doesn't go off. I woke up at 5:45. Thought maybe I snoozed or turned it off. However, the status still shows it as "on". Did a quick check, set an alarm for 6:00. It went off, and the status went to off. I can only assume that the 5:05 alarm never went off.
Read up on all the Connect sync related bugs. Don't think it's related. I disable sync during my sleep and generally only turn it on when I'm going to sync with the phone. Checked the setup in Connect and sure enough, the 5:05 alarm is still active as (Once) and all others are off.
One weird thing I noticed. The alarms do not honor the Sounds "Tone and Vibration" setting. The 6:00 alarm had "Tone and Vibration" set but only used the vibration. Anyone else seeing unreliable alarm behavior?