Recently I worked on advance system config form field in Magento 2. I checked Braintree payment method for reference.
When I saved a value, it showing following error:
Something went wrong while saving this configuration: Notice: Array to string conversion in
E:\wamp\www\magento2\app\code\Magento\Config\Model\Resource\Config\Data.php on line 38
$object->getValue() array is printed with error:
(click screenshots to enlarge)