I initially had major problems 1080p MKV files via DLNA on my Samsung LED TV (Samsung - UE 40 F 5370) to stream smoothly from my server. I suspected that Samsung Link was responsible for this or any error on my server. However, it turned out that this only the 2.4GHz network was responsible. After changing to a 5GHz WLAN with my Fritzbox the problem was solved immediately.
If someone has similar problems, just try 5GHz. When one knows that the stick is very good.