Batch API: What am I doing wrong?
$operations[] = [
  '\Drupal\drp_broadcast_videos_importer\Controller\ImportController::processBatch',
  $chunk,
];


In the above, $chunk is the list of parameters that will be passed to the batch process method. So if $chunk is an array of 5 videos, your method signature would need to look like this to match.

static function processBatch($video1, $video2, $video3, $video4, $video5, &amp;$context) {


That's probably not what you're hoping for. To fix, just wrap $chunk in array:

$operations[] = [
  '\Drupal\drp_broadcast_videos_importer\Controller\ImportController::processBatch',
  [$chunk],
];


Now your process method signature looks like this:

static function processBatch($videos, &amp;$context) {


And you just need to loop through the videos in each operation.