esaProbeHistoryOutOfSeqErrs is a 64-bit performance counter counting packets that arrived with a sequence number less than or equal to the last one seen, for a completed interval that has already closed and been archived into the rolling history log; it does not apply to Y.1731 probes. Out-of-order arrivals point to a reordering issue in the path, such as load-balanced links delivering packets on different latency routes, which a technician needs to separate from genuine packet loss before assigning a root cause. For example, a pattern of out-of-sequence packets appearing only in archived bins during business hours suggests the reordering tracks with a traffic-dependent routing change, not a constant fault.