For resolutions not 1080p (exactly 1080 horizontal pixels) and 4K the native player does not switch to 23.976 / 24 mode. This will be fixed in future firmware, probably initially by upscaling 720p 23.976 to 1080p 23.976 as some other products do (notably all Popcorn Hour).
In native Kodi no auto-frame switching works. However, this recently developed add-on will add auto-switching to Kodi, including upscaling 720p 23.976 to 1080p 23.976: http://www.futeko.com/newforum/index.php?topic=1015
The disadvantage of that add-on is that performance is not as good as with Himediaplayer app and it doesn't support 4K or HD-Audio. But work is ongoing so it may improve and gain features imminently.