[fritsch]

Here's the debug log, after reboot playing the two sample files:

1. H.264 1080p/23.976 (MKV)
   
2. H.264 1080p/24.000 (MKV)
   

http://ix.io/18dR

@Milhouse: Yes "adjust display refresh rate" is on, and working cause it switches TVHeadend footage. 

You don't have a 24.0 Mode - therefore it will stay on 60 hz for this video.

But this:

21:28:19.532 T:140681716432256 DEBUG: display width: 1920 vs video width: 1920
21:28:19.532 T:140681716432256 DEBUG: display fps: 23.977369 vs video fps: 23.976025
21:28:19.532 T:140681716432256 DEBUG: display flags: 0 vs video flags: 0

is wrong. The code tries to computer the float directly and matches too many numbers behind the "." therefore it won't match. It should try to do something like:
if (int) (fps * 100) == (int) refreshrate * 100) - that way it would only match two positions after the "."

Though - what I wonder: Your refreshrate - is that again hand tuned? It's quite wrong :-)