Morning Guys,
Just to provide some clarification from my side, my TP-Link TG3468 is the only NIC that has issues with my PCIe rissr. My Intel E1G42ET is also PCIe 1x, like my TP-Link NIC, except it works fine with the riser. My 2 older server cards (linked higher up this thread) are both PCIe 4x & work fine with this riser, taking into account the instability issues they have with this particular model of S920.
The TP-Link NIC I have is Version 4, same as @geo999 & works fine when directly connected to the PCIe slot on the motherboard. Based on all the troubleshooting we have done in this post, both the Intel E1G42ET & TP-Link TG-3468 NICs will work on my model of S920, with my testing being an iperf3 at 850-920mbps for 2 minutes.
I believe that @geo999 is onto something with the power PCIe pins. My theory is that the TP-link NIC is using a different pin for power, since 3 NICs work without issue. As a control, all NICs were plugged into a completely different PC, where all powered up & endured my 2 minute iperf3 test without issue.
If you'd like me to do any further testing feel free to suggest ideas.