Screen format - picture width when using 'fit'.

[aussiekiwi]

I have a problem with the screen format in the media player.  I have the 3.0.2 firmware version and I don't think the problem was in earlier versions.
I have the format set to 'fit' however when I play a mkv video 1920x1080 I get thin black bars at the sides.
If I bring up the controls - pause, stop etc it displays the full width. (Therefore I don't believe it is an issue with the tv - and it doesn't occur with another brand of player I have.)
If I change the format to 'full' the video plays full screen as expected.  (I would prefer not to have to change it every time in settings.)
If I use Kodi with the wrapper installed it displays the 1920x 1080 video full width correctly, and theatre format 1920x800 correctly with black top and bottom - however the playback is not as smooth as with the HiMedia player.

Any suggestions?