Hi. I had a similar issue. I had an alarm from a few days previous wake me up today although I did not have the alarm turned on.
Firstly let me say how much I love these sleepbuds - got them for christmas.
However I set an alarm, 8:45am, which was fine the first day. The second day however it went off at 2:45am. Nothing had changed. I have turned it off now as I don't want to run the risk of losing sleep worrying about whether the alarm will go off or not
Unfortunately there's not much more I can tell you guys - only that absolutely nothing had changed on the phone - it was charged bluetooth on etc. The sleepbuds were freshly charged 100% before bed.
I really wish there was a sound of rain though - it's strange that there isn't an option for that. However static noise does the job. Slept like a baby (apart from that one early wakeup).
One thing that comes to mind is that there's an option to wake you early if the battery charge is low. There's been an ongoing issue where you take them out of the charger it says 100% but in fact the battery is nearly dead. Bose will first have you update the charging case, but for me that didn't help and they did a free exchange.
What I suggest is, if it happens again, open the app and see what it says the battery level is (not that I'd trust it). Also, I think one has to explicitly enable the option so this may not apply.