My alarm is also not working on Mi note 3 on rom 8.4.26, it just did not ring in the morning, just had the notification, but not only that, the setting of the snooze interval is with problem, when selecting 5 minutes when you wake up , it changes to 10 minutes, and when it glues in 1 minute, it changes to 5 automatically. I tested and in the English language this problem of nap does not happen, but in Portuguese, yes. Please fix it as soon as possible, alarm is one of the most important apps.