Server Version#:1.22.2.4282
Player Version#: LG WebOS: 5.13.0, Platform: 4.3.0 - Samsung Smart Hub: Plex app version 2.012
Playing MKV files with chapters breaks resume/seek (timeline), the video plays from the beginning and selecting chapters or skipping ahead (seek) on the timeline has no effect.
Problem is only on LG WebOS and Samsung Smart Hub - it works correctly with Android App and Plex for Windows.
I tried removing chapters using MKVToolNix and the problem is gone.