Sonoff SNZB-03 is sending MQTT messages but has state of "Unknown"

I have a few Sonoff SNZB-03 Zigbee PIR sensors, working with a (Tasmota’d) Sonoff Zigbee Bridge using Z2MQTT. Since Wednesday one of the sensors stopped triggering my HA automation. When I checked its state it shows as “Unknown”, but when I look at the console on the Sonoff Zigbee Bridge I can still see messages from the sensor when it’s being triggered. It was working fine in HA until 2 days ago.
This is how I have the binary sensor configured:

#PIR in Study
  - name: "PIR study"
    state_topic: "tele/zigbee-bridge/SENSOR"
    value_template: "{{ value_json['0x48AD'].ZoneStatusChange }}"
    device_class: motion
    qos: 1
    payload_off: '0'
    payload_on: '1'

…and here’s a line from the Sonoff ZB Bridge 10 minutes ago:

11:08:11.529 MQT: tele/zigbee-bridge/SENSOR = {"ZbReceived":{"0x48AD":{"Device":"0x48AD","Name":"pir-study","0500<00":"010000010000","ZoneStatusChange":1,"ZoneStatusChangeZone":1,"Occupancy":1,"Endpoint":1,"LinkQuality":68}}}

Any idea why HA has stopped seeing the SNZB-03?
(I’m running HA 2023.2 Core)