pi3 1080i liveTV delayed

Hey guys,

I have installed libreElec on pi3.
Actually I encountered two problems:
a) when I play 1080i liveTV I see that audio is getting more and more out of sync (video too slow)
b) the gui is quite slow and stuttering while video is playing in background.

Is there any way to use a pi3 to playback smooth video up to 1080i 50 Hz or should I use a different hardware?

CU
mts