Bluetooth Proxy Tracker Sensor Template

Hello,
this code stopped working a couple of weeks ago (It worked before that), now I only get the “N/A” value, although the device is connected properly to the bluetooth proxy.
Can anyone see something weird or unsupported code?

      bt_state_pixel_6:
        friendly_name: "Bluetooth Location Pixel 6"
        value_template: >-
          {% if is_state_attr('device_tracker.bt_pixel_6', 'Source', '78:21:84:9d:d0:78') %}
            Obergeschoss
          {% elif is_state_attr('device_tracker.bt_pixel_6', 'Source', '78:21:84:9d:e2:18') %}
            Wohnzimmer
          {% elif is_state_attr('device_tracker.bt_pixel_6', 'Source', 'ec:62:60:9c:af:cc') %}
            Keller
          {% elif is_state_attr('device_tracker.bt_pixel_6', 'Source', '00:1A:7D:DA:71:10') %}
            Eingang
          {% else %}
            N/A
          {% endif %}