OSD not appearing until video playback finishes

New to OSMC and the Pi, but not new to Kodi or Debian.

Got 2016-04 up and running almost perfectly. Problem is that the OSD does not appear when pausing the video or pressing a button that should trigger it, e.g. changing subtitles. Also the subtitles themselves do not appear.

When I stop the video, all the notifications that should have popped up all appear rapdily one after the other, for example if I start a video, then press the cycle subtitle button multiple times and then stop it. It’ll flash up e.g. Subtitles: Forced -> Subtitles: English -> Subtitles: French -> Subtitles: Disabled -> Subtitles: Forced in quick succession while on the list of movies.

Tried it with no acceleration, MMAL, OMX and both, makes no difference.

Tried with the OSMC skin, confluence and amber, no difference.

Any idea what the problem could be?