No subtitles when embedded in mp4 and playback via Apple Composite AV cable

I’m using an iPad 3rd gen (iOS 8.3, latest Infuse) and an Apple Composite AV cable ( to playback videos on TV.

I noticed that when an mp4 file has embedded subtitles these won’t show when playing on the TV. When the cable is not plugged in and the video is played on the ipad, the subtitles show fine and can be toggled.
When I add a srt file, the subtiles show on the TV.
Tested on two different TVs.

*.mkv files with subtitles show fine as well.

I think I noticed this almost a year ago, so probably still with iOS 7.x and whatever version Infuse was at back then. But I had to delete the files and had no time to report this before. Also those mp4 files with embedded subtiles are not that common. I had to search a bit for some. If you have access to usenet I can point at an example per PM.
It’s not an immediate problem for me, just wanted to let you know that there is something off.

I know you looked into this, no idea what the status is as I’ve lost the cable during a vacation :frowning: