What caused my false alarm?

I have been using the alarm system for about 3 months now with out any issues. Last night for no reason the motion sensor in my wife's office set off the alarm. Closed room, no people, no pets, no lights, no heat source. I have not had this issue before and I can't duplicate it for the life of me. I have read the other threads about disconnecting and reconnecting, watching for heat sources, other best practices; but what caused this? I have heard of insects crawling over sensors setting them off, but I didn't think that was the case with the sensors used in the Ring 2nd gen sensors. I would really like to have an explanation for what happened. I have a hard time trusting a system without a good explanation of its limits and I want to trust my alarm system.Side note to the alarm being triggered: I have two devices (Ring outdoor security cam, and Ring doorbell) linked to the alarm, but only the security cam recorded a linked event when the alarm was tripped. Any ideas why the doorbell (which is otherwise working properly) did not record a linked event?