Hello!
My Venu 3, which is barely a month old and has the latest firmware installed is doing something weird with the alarm. Specifically, the first alarm of the day. I have a Weekday-repeating alarm at 5:45am using vibration only which is also the end of my sleep period. When the alarm goes off, the watch vibrates once and then the alarm cancels itself. If I try to recreate it for any other time after the initial wakeup, the alarm acts as expected. Possibly related, I disabled the morning report prior to this beginning.
If Garmin support wants to contact me by email about this issue, you have my permission to do so.