Some preview urls for tracks that are populated using user authorisation are null when using app authorisation

[PyroPez]

Issue found on May 8th 2020.

Endpoint(s):

• GET https://api.spotify.com/v1/tracks/
• GET https://api.spotify.com/v1/playlists/{playlistId}/tracks

Scope(s):

• App Authentication
• User Authentication (no additional scopes)

Steps to reproduce:

1. Get authentication token using user authentication
2. Send GET to https://api.spotify.com/v1/tracks/68TJaMSstlIuOKpRr1riov?market=GB
   Preview url returns with a value
3. Get authentication token using app authentication
4. Send GET to Send GET to https://api.spotify.com/v1/tracks/68TJaMSstlIuOKpRr1riov?market=GB
   Preview url returns as null

Expected behaviour:

Preview url has a value when using both user and app authentication

Actual behaviour:

Preview url is always null for some tracks when using app authentication but not when using user authentication

app-authentication-response.txt
user-authentication-response.txt