please try to load the latest driver of i218-V for your system, you can check the link below:
if problem still persists, try setting the "gigabit master slave mode" on advanced properties of your network adapter to "force master mode".
the ethernet cable you're using should be CAT 5e or higher to ensure gigabit connectivity.
hope this help.
I have a similar problem. I can only do 10 Mpbs Full with powerline ethernet adapters. 100 Mpbs negotiates, but ping times are 2-3 seconds. I have 3 different powerlne adapter brands and all of them have trouble with my new T450s. I have atleast 3 different PC and laptops at my home and none of them have trouble with the powerlne adapters. I checked other forum threads and this problem seems to be open.