An inbound email that comes from a mailing list is automatically going to not autoreply to prevent looping.
We of the mailing list can't have access to your logs, and our crystal ball gets a bit fuzzy. If OTRS says it sent no Auto Reply, when does it stop? Does it stop forever, for all incoming tickets? Does it stop for a specific ticket/sender that it replied to before? Does is stop for a specific sender that it autoreplied to before but never autoreplies again? Does it stop for a specific ticket or response and then work again for a new ticket or response?