receive higig2 Ethernet packet

Device:10AX115S3F45E2SGE3 quartus16.0

When i use ipcore"Low Latency 40G/100G Ethernet" receive higig2 Ethernet packet.Some times ,the ipcore output startofpacket data "fb 00 00 00 00 ...",the "00 00 00 00" is not right data.And the FCS bytes of endofpacket is wrong when calculate including "00 00 00 00" .When the "00 00 00 00" calculation is not included, fcs is correct .And the receive package number is less than send.How to deal with it ？Thanks.