Looks like a temporary thing - maybe just treat it as a retryable failure?
But if we get a lot of them in a row, we'd just needlessly increment failure counts on subscriptions - maybe stopping the charge job run and trying again in 20 min is really the best handling.
Request returned http status (503): {"status":503,"errorCode":"703","message":"required resource temporarily unavailable","errorType":"internal"}
REST capture request threw exception!
SmashPig\Core\ApiException@PaymentProviders/Adyen/ExceptionMapper.php:321 (Unknown Adyen error code 703)