Playback interrupts on Synology DS212j and Samsung ES6300

Hi,
Today I got my new NAS and because I don't like the internal Video-Streaming-Service, I installed serviio.
The installation was quite easy and it successfully indexed all my movies and series.

But now I have the following problem: If I watch via my Samsung smart TV UE40ES6300 the playback stops several times
and the player closes itself. The problem appears sporadically, so sometimes I can watch 30 minutes without any problems
and sometimes the playback stops every 2 minutes.
On my galaxy S3 and the ServiioGO App this problem does not occur.

I'm a bit lost here, does my NAS may not provide enough capacity or is it really a network Problem?

Hope you guys can help me.
greetings.

PS.:
I tried the following things.

watching the same clip on TV and Smartphone: TV interrupted, smartphone not
pinging the NAS while watching: no abnormalities while the TV stopped.
UPnP is activated and the NAS is the only UPnP device in my Network

On my PC serviio worked without any Problems for weeks.

The NAS is not fully occupied but it has to do well with Java so the RAM and CPU are always around the 85% mark

I have the same problem with Sony Bravia kdl 46ex521. My servvio work fine whit my iphone 5 and ipad with 8player lite (i can see .mkv too). The TV in wired mode, so i don't think that the network is the problem.

Someone have a solution ????

I forget to say that the my server is d-link dns 320. Different device but the same problem. thank's at all.