Before processing a message in a subscription, the following check must be performed:

[marcschier]

Before processing a message in a subscription, the following check must be performed:

(!State.SequentialPublishing || ValidSequentialPublishMessage(ii.Value))

and ValidSequentialPublishMessage:

{
    // If sequential publishing is enabled, only release messages in perfect sequence.
    return message.SequenceNumber <= m_lastSequenceNumberProcessed + 1 ||
        // reconnect / transfer subscription case
        m_resyncLastSequenceNumberProcessed ||
        // release the first message after wrapping around.
        (message.SequenceNumber == 1 && m_lastSequenceNumberProcessed == uint.MaxValue);
}

Here, a message with an outdated SequenceNumber can be accepted.
I tried to simply change it to: (message.SequenceNumber = m_lastSequenceNumberProcessed + 1),
It caused side effects and I abandoned the idea of ​​fixing it right now.

Originally posted by @AnatolyKochnev in #3565 (comment)