I had running CoreELEC for weeks. It run very well. But even with the newest 8.95.7 I have this buffering issues when watching live-tv only with 720p HD channels (german tv channels ARD HD, ZDF HD and so on).
You wrote "...Tvhead works for me..." You have a tvheadend tv server? And with tvheadend even 720p HD channels are working? I have a Windows 7 pc with mediaportal tv Server 1.17. My hardware combination is not working.