D-ID API tried to download image from my audio URL

curl --request POST
--url https://api.d-id.com/talks
--header 'accept: application/json'
--header 'authorization: Basic API-Key-Base64'
--header 'content-type: application/json'
--data '
{
"script": {
"type": "audio",
"provider": {
"type": "microsoft",
"voice_id": "Jenny"
},
"ssml": "false",
"audio_url": "https://objectstorage.oraclecloud.com/.../audio.m4a"
},
"config": {
"fluent": "false",
"pad_audio": "0.0"
},
"source_url": "https://objectstorage.oraclecloud.com/.../image.png"
}
'

The API replied:

BadRequestError: cannot download image from https://objectstorage.oraclecloud.com/.../audio.m4a - may be corrupted or does not exist

Which is clearly wrong, it didn't download image from the source_url, but from the audio_url. When I switched the values of them, I got a validation error.

so, what happened? I literally copied the code from d-id doc's generated script.