Plex keeps buffering

[curantil]

Server Version#: 1.15.6.1079 (On Synology DS918+)
Player Version#: 2.005 (On Samsung UE32H6400 smart TV)

Recently a lot of my video seems to periodically buffers. Also for videos I’m pretty sure didn’t buffer before.
If I check the verbose log, the speed is 0,7 (even with ultra fast background transcodig), but CPU usage is almost 0%. Network traffic is also low. I tested network speed with iperf3 and it reports a bandwidth of 50Mbit/s. I have hardware acceleration enabled for transcoding.

I also get more problems finding the server when I start the app on the TV.

I checked seen the guide concerning buffering on the support pages and I have seen a lot of topics on buffering, but I didn’t find a solution in there yet.

Any ideas what the problem could be?

[curantil]

Here are the requested logs and xml:
Plex Media Server Logs_2019-05-30_14-16-54.zip (2.5 MB)
movie.xml.txt (35.8 KB)

Since the buffering happens less than a minute apart, I stopped (paused) the playback right after a buffering period. The buffering happen a few times in the span of the logs.
Thanks

[curantil]

But the CPU graph shows almost no processor usage while it is buffering?
Below is a screenshot from when it is busy buffering.

I have configured the client to limit the bandwidth, so I assume it is a default behavior for the app. I cannot find any settings related to that.