Ubuntu 16.04. PMS 1.2.7.2987-1bef33a from the ninthgate ppa.
On Nov 14, I updated Ubuntu for the first time in about a month. The update installed PMS 1.2.7.2987, among other things. Videos that played on Roku with subtitles before the update do not play after the update.
Videos do play on Roku if I turn the transcode option off automatic to DirectPlay with Fallback, but without subtitles. Videos do play on automatic if I turn subtitles off. The same videos do play in VLC and from the Plex Webapp with subtitles in Firefox, both on Windows 7. I'm using the Plex Classic Roku app because I prefer it and don't allow access to my server from outside my home network, so no need for the new account-bound app.
I'm using two media files as examples. This issue affects other, similar files.
File 1 is an MKV container. VLC reports the stream codecs as Video: H264 - MPEG-4 AVC (part10) (avc1); Audio: MPEG AAC Audio (mp4a), Subtitle: SubStation Alpha subtitles (ssa).
File 2 is an MKV container, Video: same, Audio: same, Subtitle: BD subtitles (bdpg).
Please don't say it's the MKV format or the subtitle format. These files played with subtitles on the Plex Classic Roku app with no problems before the update. I've confirmed that the drive mount options are as they were before the update (ext4 rw, noatime, nodiratime,nobarrier,errors=remount-ro) and that Plex does have access to the files (both by inspecting permissions and confirming the plex user is a member of the a group that has rwx access and by playing them without subtitles on certain settings described earlier).
I've inspected the logs (Plex Media Server.log and com.plexapp.system.log) and see no errors between starting the play attempt and the play attempt failing. Grepping for ERROR shows only a handful of errors, none of which describe transcoder failures.
I'm attaching a clean Plex Media Server.log (stopped PMS, cleared log, restarted PMS) that shows a play attempt for DirectPlay with Fallback (file plays, but without subtitles) and a play attempt for Automatic transcoding (file fails to play). What other information can I provide to help find a solution to this problem?