Image Files Uploaded via REST got Temporary status - Cannot be refereced by Media Image
The solution I found so far is to fix a Drupal module code:
modules\contrib\file_entity\src\Normalizer\FileEntityNormalizer.php
on line 48 add:
$entity-&gt;setPermanent();

See:

Which Drupal 8.1.x Rest API property in the JSON request controls
Drupal's File status (Temporary and Permanent) logic?

Files created with REST API are only temporary