The leak sensor under my guest bathroom sink detected a leak two nights ago. And consequently the water main shut off. The sensor switched to reporting dry later in the night. When I woke up and looked under the sink the next morning, it was dry, convincing me that the sensor (Aqara Leak Sensor) was misreporting or needed a new battery. I changed the battery, and for good measure, removed and re-added it.
Just now, I used the guest bathroom sink for a little bit and got a notification that the sensor was wet. Sure enough, I found a very slow leak from the pop-up drain assembly that ran down the drain and drops of water fell every 1-2 minutes from the lowest point on the P-trap. The sensor is positioned directly below the P-trap and was being triggered appropriately.
So no doubt the sensor was right the first time also .... the few drops of water had just evaporated by the morning.