Server Version#: 1.15.6.1079
Player Version#: 3.100.1
Simply put, when a video has VOBSUB External subtitles, the player does not start a Transcoding process on the server and playback crashes in the player. Starting and playing the video without using those subtitles plays the video fine, the transcoder process begins on the server. Switching to the subtitles also stops the transcoder process and the video fails to play. This does not happen with srt subtitles. This only happens on the web client, not the dedicated player software. Tested in both Chrome and Firefox.
EDIT: This is reproducable on the Android app as well.