I have two RJ45 wall jacks that run from where the PCs are located to two wall jacks near C50 in a different room. Given the findings of the prior test, I replaced the patch cords in both rooms with brand new patch cords. One of the Ethernet runs is used to connect the PC to the C50 admin port, the other is used to connect the PC to the LAN port of the DUT so I can monitor the DUT. Both of these runs are rather long, but I believe they are in spec (less than 100 meters).
I ran my original Wifi test, 2Gb/s 1518 byte UDP traffic from a 10GbE C50 Ethernet port thru the DUT to the 6GHz 4x4 client on the C50 using the newer PC. It failed after several hours (GUI hang again). Then I swapped the connections for the C50 admin port and DUT LAN port so I was using the second structured wiring run. I ran the test and it failed the same way after several hours.
I realized that for the longest time, I had been using an old Cisco Gigabit switch near the C50 since I had a second demo C50 and only one Ethernet connection for both C50's.
I ended up putting it back, taking the admin connection from the C50 into one port of the switch and the wall jack patch cord to a second port. I restarted the test and it has been running error free for over 24 hours.