Thanks for your suggestions and insight, @andrewwynn . Once I get the car back from the shop (assuming they're able to replace the recently swapped out IMS for a new one, under warranty) I did want to run an experiment of parking the car inside the garage to see if that makes a difference. Perhaps I can setup a time lapse camera as well.

At first I thought it may have been a bug inside the car, but then I would've expected the alarm to go off at random times, not just on random mornings around the same time.

Then the recent time when the alarm triggered right before noon after I flipped the car's orientation 180 degrees really threw me off as that was the first time the alarm went off so "late" compared to its normal ~8:20-8:30am triggering.

I know I can workaround this issue by double locking, but I really want to get this fixed if I can...