I have my alarms set for every day of the week at the exact same times, excluding weekends.
Monday this week I woke up to find I was late, my alarms had not woken me up, and there was no "missed alarms" notification.
Both Tuesday and Wednesday, the alarms had gone off.
This morning, I was awake before my alarms, and I noticed that they had not gone off, nor are there any missed alarm notifications.
I had one left that I turned off and on again, and it did just go off, but I'm worried that I need to reset them 10 minutes before I use them in order for them to work properly.
Copied my phone from my S9 Edge, which did not have this issue.
Unfortunately, I do not have DnD on. But I will attempt deleting and recrreating all my alarms.
Solved my issue, thanks man!