[Ubuntu 16.04] Plex won't play media when finding invalid data in automatically downloaded subtitle.

I am having and issue with Plex Media Server 0.9.16.6.1993-5089475 amd64 on Ubuntu 16.04 where this issue is happening:

Plex automatically downloads subtitles, and when playing media with some of those subtitles the media won't play at all. It plays just fine without the subtitle.

I saw some others having this problem and they changed the locale, but that does not seem to be the problem here as the locale is set in the plexmediaserver systemd unit file through LC_ALL and LANG, and I have en_US.UTF-8 available on the system:

$ systemctl cat plexmediaserver
...
Environment=LC_ALL=en_US.UTF-8
Environment=LANG=en_US.UTF-8
...

I checked the logfile and found the subtitle file it tried to use while seems to be a gziped file:

$ sudo -u plex file "/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Media/localhost/0/406a7fe73efc276a59f093928812ecc85c68f8a.bundle/Contents/Subtitle Contributions/com.plexapp.agents.opensubtitles/en/d19721416d7d5a7c3ad7d370eb3cb717a9e905c1.srt"
/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Media/localhost/0/406a7fe73efc276a59f093928812ecc85c68f8a.bundle/Contents/Subtitle Contributions/com.plexapp.agents.opensubtitles/en/d19721416d7d5a7c3ad7d370eb3cb717a9e905c1.srt: gzip compressed data, max compression, from Unix

Uncompressed it seems to be a normal text file:

$ file gunziped 
gunziped: UTF-8 Unicode (with BOM) text, with CRLF line terminators

I would just assume that the problem is the compression of the file, but if that is the case plex should probably either not download compressed versions, be able to decompress them, or delete them when finding a compressed subtitle that is automatically added.

PS: I am not allowed to upload the compressed subtitle file.