I am using a Optcore 2.5GBASE-T SFP Transceiver Module in a custom configuration with an Armada 3700 SoC. 99.99% of the time it is working perfectly. However, I just diagnosed a failure which seems to be in the SFP module. It is very reproducible. When a packet is transmitted from the SoC that contains a sequence of 20 octets with each octet being 0x4a, the transceiver fails to transmit that data. I have isolated this to the SFP module by connecting the SoC directly to switches that accept SGMII differential pairs directly and the issue goes away. Furthermore, packet traces on the SoC show successful transmission, but packet traces on the client do not show reception. I can provide packet traces and small client server program which demonstrates the issue.