I see that a driver was recently released to address an issue with SEP and sleep. I have this driver installed on my laptop, a Lenovo T450s, driver version 12.12.80.1950. I have not experienced the problem that this driver was to correct, so I suppose that it is indeed fixed. However, I am experiencing another problem that perhaps this driver may have broken.
It seems SEP 12.1.5 has a problem with this card/driver and file transfers. If I initiate a transfer of several hundred MB or a couple GB then it'll copy about 10 MB and I'll lose the Ethernet connection. A reboot will get the NIC working again and this problem does not effect the wireless. It'll also drop off while surfing the Internet, not downloading anything but the websites, so the size of the download doesn't play a role. Uninstalling SEP also fixes the problem, though I must have antivirus on our corporate computers.
Any ideas out there?