Mailbox sensor stopped sending Motion Detected events

Up until 3 days ago, any time the Mailbox Sensor triggered, I got 2 events. Motion Detected, followed by Stopped Detecting Motion. I had Alexa turn on a light and announce "mailbox opened" in response to motion. Now it only sends "Stopped Detecting Motion." The "Motion Detected" no longer occurs. Alexa does not respond to "Stopped Detecting Motion." So effectively the mailbox sensor no longer works with Alexa. I've tried deleting the sensor from the app and re-installing it, and deleting the Ring skill from Alexa and re-installing it. Nothing changed.