i've been able to consistently reproduced the issue. no luck ID'ing the specific cause, yet.
fyi, i've asked as well @ http://postfix.1071664.n5.nabble.com/local-postfix-re-delivery-of-dovecot-sieve-redirected-mail-fails-normal-direct-deliveries-are-OK-td107691.html with slightly simple config and cleaner log detail.