Battery level updates, then disappears

I setup owntracks on my phone and I have Home Assistant displaying my battery level. It’ll work for a little while and display the percentage in the circle on the states page. Eventually it displays nothing, just an empty white circle. Any idea what’s happening?

sensor battery:

  • platform: mqtt
    state_topic: “owntracks/bdog/garb”
    name: “S6 Battery”
    unit_of_measurement: “%”
    value_template: ‘{{ value_json.batt }}’