I've created MKV's with MakeMKV 1.6.14 from a DVD and a Bluray, put them on the QNAP serving it to my Samsung TV. Result was that neither MKV could be played. After googling a bit I found out that the Samsung TV's seem to be a bit picky in respect to the MKV's. After I've used the mkclean tool from matroska.org, my TV did not complain anymore and played the MKV.
It would be nice if future versions of MakeMKV would directly create "clean" MKV's that are accepted by the Samsung media player.
Can you please create an MKV file with makemkv, use mkvmerge and cut a small portion (10 seconds or so) out of MKV file, save as file1.mkv . Confirm that it doesn't work, fix it with mkvclean, confirm that it works and then send file1.mkv to support@makemkv.com with a link to this post.