No video Audio only

Almost all my media plays without issue but there are a handful that have audio and just a black screen.
Is there any solution to this? They are mkv files.
Playback issue only shows up on my firestick v2 but works everywhere else.

HEVC h.265 playback may not be supported on your device.
You can try changing the Video decoder to Software or Hybrid in the Channels app settings.

Else, re-encode those files to h.264.

Thanks for the reply.
I am not sure where this "Video decoder to Software or Hybrid" in the app is found but just for fun I turned deinterlacing on and that seemed to do the trick.
Just not sure if that will impact anything else. I guess time will tell.

In the App Settings, it's under Playback > Advanced > Video Decoder.