Server Version#: 1.23.5.4841
Player Version#: 6.8.3.7132
Roku player will occasional not display a subtitle.
Most subtitles show up correctly. Mac and PC players show subtitles 100% correctly from the same server/file. It SEEMS that it will drop the subtitle when the time gap to the next subtitle is long (e.g. 20min).
Additional info: file = mp4, type = mov_text, added using ffmpeg to merge streams.