[Gee11]

I would say it's an issue with the stream itself, or possibly with access price on your server:

Code:

22:16:53.197 T:5924 NOTICE: AddOnLog: MediaPortal PVR Client: Cannot access 'X:\\live11-0.ts.tsbuffer' directly. Assuming multiseat mode. Need to translate to UNC filename.
22:16:53.197 T:5924 NOTICE: AddOnLog: MediaPortal PVR Client: Translate path X:\\live11-0.ts.tsbuffer -> smb://xxxx:xxxxxx@SERVER/Timeshift/live11-0.ts.tsbuffer

22:16:53.514 T:5924 WARNING: CVideoPlayer::OpenStream - Unsupported stream 0. Stream disabled.

Also you've got Kodi running with admin rights, which is neither required nor recommended.

The log also contains your server login credentials, so may need redacting (it also doesn't have debug log enabled). 

But it cant be an issue with the tv stream. It works with Kodi 17 mepo tv plugin. And movies with mutch higher bitrate plays fine also. I think its the buffering on tv streams that changed in Kodi 18. Maybe Marcel Grootis can help me here

[Gee11]

Live TV via RTSP works. But without timeshift. When i press pause Kodi crashes and i have to restart it. Also when i switch channels it dosnt work. I have to stop live tv before switching the channel.

[steo86]

same problem here. Kodi 17 worked without suttering. Now with kodi 18 stuttering especially with channels 720p/50frames (german channels "zdf hd" and "ard hd").
Channels with 25 frames seems to work without any problem. When enabling RTSP then all channels seems to work but then timeshift ist broken.

[steo86]

Problem does not seem only related to Mediaportal. Just installed ArgusTV-Server on my Server for testing.
Problem is the same. Stuttering and Buffer ring when running LiveTV. Then I recorded the same channel.
The recording can be played without Problems (not Buffer ring) via the "Movies"-Tab in Kodi.
So the Problem seems to be related to the way data gets buffered in kodi 18. 
It seems that most TV-pluggins (Mediaportal and Argus) can not handle that in Kodi 18.