We're talking about MKV files, right?
Both the browser and OSD are in error in that they report 23.976 as 29.970.
Playback is wrong in the sense that 23.976 hz is not transmitted as such, but is converted to 60hz via standard 3:2 pulldown. The video is correct as a 60hz signal, but not what the user wanted. This is a regression from previous firmware.