'TCP out-of-order' - This occurs when a packet is seen with a sequence number lower than the previously received packet on that connection
from wiki:
out-of-order delivery is the delivery of data packets in a different order from which they were sent. Out-of-order delivery can be caused by packets following multiple paths through a network, by lower-layer retransmission procedures (such as automatic repeat request), or via parallel processing paths within network equipment that are not designed to ensure that packet ordering is preserved. One of the functions of TCP is to prevent the out-of-order delivery of data, either by reassembling packets in order or requesting retransmission of out-of-order packets.
You can use 'monitor capture' on router or wireshark capture at one end of the tcp session
