Hi tmmoore800, you may try to disable the "energy efficient ethernet" found in your advanced tab of realtek ethernet controller on your DN2820FYKH
moving your question to NUC forum, members in that forum might be able to provide additional info to assist on your issue.
The bottleneck could be the router, a consumer router hardly can manage 700Mbps. A Netgear R7000 has NAT-LAN routing capability around 450Mbps (Stock Firmware). To get full advantage of you excellent line I would suggest server grade router.
Thank you for your suggestion. I placed the question on the NUC forum. I think I tried the energy option but will check again.