Momentary piezo occasionally doesn't stop

I've got a piezo set up as a warning signal while the alarm is in pending state. Sometimes it works fine, but about 25% of the time, when the alarm changes to another state, whether triggered or disarmed, the piezo stops chirping and starts buzzing full time. I can turn it off manually with a switch, but on its own it will just keep buzzing.

I've seen a few other threads reporting problems with piezos, but not exactly this. My configuration is below, I'd appreciate any suggestions.

konnected:
  access_token: !secret konnected_access_token
  api_host: http://<etc>
  devices:
    - id: <####>
      host: <####>
      port: <####>
      binary_sensors:
        - zone: 1
          name: 'Front Door'
          type: door
        - zone: 2
          name: 'Front Door Motion'
          type: motion
        - zone: 3
          name: 'Garage Door'
          type: door
        - zone: 4
          name: 'Garage Door Motion'
          type: motion
      switches:
        - zone: out
          name: 'Siren'
        - zone: 5
          name: 'Front door Piezo'
          momentary: 150
          pause: 500
          repeat: -1 

automation piezo:
  - alias: 'Beep piezo while in pending state'
    trigger:
      - platform: state
        entity_id: alarm_control_panel.home_alarm
        to: 'pending'
    action:
      service: homeassistant.turn_on
      entity_id: switch.front_door_piezo

  - alias: 'Stop beeping piezo when pending state ends'
    trigger:
      - platform: state
        entity_id: alarm_control_panel.home_alarm
        from: 'pending' 
    action:
      service: homeassistant.turn_off
      entity_id: switch.front_door_piezo