Different avatar urls, same user with /rest/api/3/user/assignable/search?issueKey=...

Michael Schmidt_bxfx9v

When I call the rest api endpoint /rest/api/3/user/assignable/search?issueKey=xxx-1 one time with AP.request from within the app iframe and one time in the browser search input then I get different avatar urls:

AP.request:

{
"48x48": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/initials/MS-0.png",
"24x24": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/initials/MS-0.png",
"16x16": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/initials/MS-0.png",
"32x32": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/initials/MS-0.png"
}

Browser or Postman:

{

"48x48": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/557058:c755c582-8f73-4432-a3e1-ffd318d0df1c/218cee7a-d9fe-4869-a451-1910575df8d5/48",

"24x24": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/557058:c755c582-8f73-4432-a3e1-ffd318d0df1c/218cee7a-d9fe-4869-a451-1910575df8d5/24",

"16x16": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/557058:c755c582-8f73-4432-a3e1-ffd318d0df1c/218cee7a-d9fe-4869-a451-1910575df8d5/16",

"32x32": "https://avatar-management--avatars.us-west-2.prod.public.atl-paas.net/557058:c755c582-8f73-4432-a3e1-ffd318d0df1c/218cee7a-d9fe-4869-a451-1910575df8d5/32"

}

It's the same user. Why don't I get the image of the user in the first case?