Adding custom configs breaks helmRelease

I installed a default NC helmRelease from Stackspin on my cluster, and then added an override like this:

apiVersion: v1
kind: ConfigMap
metadata:
  namespace: stackspin-apps
  name: stackspin-nextcloud-override
data:
  values.yaml: |
    nextcloud:
      nextcloud:
        configs:
          defaults.config.php: |-
            <?php
            $CONFIG = array (
              'allow_user_to_change_display_name' => false,
              'default_phone_region' => 'DE',
              'default_locale' => 'de',
              'lost_password_link' => 'https://sso.ftt.gmbh/login/recovery',
            );

When I try to reconciliate the NC helmRelease I get:

helm-controller  reconciliation failed: Helm upgrade failed: error while running post render on files: may not add resource with an already registered id: ConfigMap.v1.[noGrp]/nc-nextcloud-config.[noNs]