TX packets loss when frame size is multiple of 4 bytes under full load on 82599

Hello,

When run RFC2544 throughput test under full load(total 4 x 10GbE ports on 2 x 82599ES NICs on E5 2697v3 Server) with Spirent TestCenter, we increased frame size by 1 byte step from 64 bytes to 1518 bytes.

There is an issue as titled, TX packets loss when frame size is multiple of 4 bytes, the attached is a test report(from Page 11).

If any idea for this issue?

Thanks,

Michael