Customize "Arrange By"?

[equalme]

On my rMBP, .MKV files are correctly sorted under "Movies" along with MP4 when I use the "Arrange By" function.

But for some reason, on my Mini, the .MKV files get sorted under "Others".

Is there a way to fix this? It's really annoying. Both are running the latest El Capitan.

Thanks!

 

[Gregg2]

Have you compared preferences on the two machines?