entity_lookup for user entity type

I’m trying to link a field in my spreadsheet file to a user that is previously created with a migration from the same spreadsheet. The Backup column consists of multiple names divided by the backward slash (Firstname Lastname/Firstname Lastname)

migrate_plus.migration.profiles.yml:

process:   field_backup:     -       plugin: explode       delimiter: '/'       source: 'Backup'     -       plugin: entity_lookup       value_key: name       ignore_case: true       entity_type: user       bundle_key: uid       bundle: people 

migrate_plus.migration.users.yml:

process:     name:       plugin: concat       source:         - 'Firstname'         - 'Lastname'       delimiter: ' ' 

The backup field is just skipped when migrating the profiles. The only error I’m getting is when i go to a profile page and check the log messages.

User error: “attributes” is an invalid render array key in Drupal\Core\Render\Element::children() (regel 97 van /var/www/html/web/core/lib/Drupal/Core/Render/Element.php) #0 /var/www/html/web/core/includes/bootstrap.inc(587): _drupal_error_handler_real(256, ‘”attributes” is…’, ‘/var/www/html/w…’, 97, Array) #1 [internal function]: _drupal_error_handler(256, ‘”attributes” is…’, ‘/var/www/html/w…’, 97, Array) #2

/var/www/html/web/core/lib/Drupal/Core/Render/Element.php(97): trigger_error(‘”attributes” is…’, 256) #3

Can you not use entity_lookup for users or am I doing something wrong in my configuration?

Any help would be much appreciated