It happened once at my mom’s church, probably around 10 years ago. I was talking to one of her friends, and I looked over at the 2903-9101 + 2901-9838 combo in the corner of my field of vision, and it went off (in continuous). Turned out one of the younger kids pulled the alarm.
Also, I frequently keep one eye on the NA if I know there’s going to be a fire drill.