Incomplete listing of internal subtitles of Matroska files
The file corresponding to the attached description lists no subtitles: mediainfo.txt
Another created with mkvmerge v35.0.0 (libebml v1.3.9 / libmatroska v1.5.2) shows only one srt subtitle out of 2.
Under Windows, a mediaplayer such as MPC-HC does detect and correctly displays the subtitles of both files. A recent LG TV set (+ Serviio DLNA server) does play all subtitles.
Probably unrelated, but I think all audio streams are correctly reported.