Stuttering Trailers

I am located in Germany and i’m getting this message (translated from German): “Your server connection is not fast enough to play video. Check your network or try a lower quality setting.”

Even if I set the quality to 64kbps this message appears. At the same time the actual 1080p movies stream fine in my network, it’s just the trailers and extras that produce this error. Strangely enough sometimes trailers play instantly and without stuttering, sometimes they stop after two seconds and buffer indefinitely, sometimes the server connection error appears.

When I’m playing any other streaming video in Plex (Youtube, play later, etc.) I’ve never experienced any stuttering.