Custom sound in non-critical notifications

Hello! I have a notification as part of an automation that’s sent to my iPhone. The automation config looks like this:

description: ""
trigger:
  - type: turned_on
    platform: device
    device_id: ...
    entity_id: ...
    domain: binary_sensor
    enabled: true

action:
  - if:
      - condition: device
        device_id: ...
        domain: device_tracker
        entity_id: ...
        type: is_home
    then:
      - service: notify.mobile_app_iphone
        metadata: {}
        data:
          title: Movement
          message: Possible movement has been detected
          data:
            push:
              interruption-level: critical
              sound:
                name: "{{ states('input_text.alert_soundname') }}"
                volume: 0.8
            tag: catcam-motion
mode: single

The custom sound (uploaded through Google Drive, the state variable renders to motion_alarm.wav) works perfectly, adjusting the volume does as well.

However - when I set the interruption-level to “active” for a “default” notification, the custom sound does not work anymore. No sound is played at all, it does not fall back to the default sound.

It DOES work when setting the interruption level to “active” and changing the sound to 3rd_party_critical.caf for example, which would be a default iPhone sound.

As I would love to manage my phone’s notifications with different focus plans, I’d really love to get custom sounds in non-critical notifications to work.

Importing sounds from iTunes did not work, the phone app kept telling me that zero sounds were imported.

Any hints I could try out are appreciated!

Best regards