Subtitles needs to be turned on in every videofile

I have a lot of .MTS video files from a Sony video camera.
It stores the time and date info in some kind of “subtitle”-format inside the video file.
Kodi can show it, but I need to manually activate subtitle in each new video file that I am playing.

Just activating subtitles and then choosing “Set as default for all media” doesn’t have any effect, as soon as I
watch the next file the date and time is lost again.

I just updated to Kodi 11.3 (on a Raspberry Pi 3) and I still have the same issue.