I have been noticing this for awhile but hadn't really taken the time to explore deeply until this weekend.

I rip and encode my BD movies to .mkv files, typically using Handbrake. For some movies I like to leave the size and bitrate pretty high. I am noticing that these larger files suffer from Jitter and Stuttering on playback with the FireTV and FireTV Stick (both v2) when using Mezzmo Android's built-in Media Player. It almost looks like a framerate issue because you only really notice it on panning scenes and during action but static scenes are good. For example, I have a 15GB .mkv of the Revenant that is almost unwatchable using Mezzmo Android's Media Player because of the large amount of panning in the first 10 minutes. If I use VLC as the media player, the problem disappears. If I use Kodi and the Mezzmo Plug-In it is also smooth as butter.

We can eliminate Bandwidth limitations and hardware resources as culprits since I have transcoding turned off and they play fine with VLC and Kodi.

I have tried it with Device Profiles set to both Kodi and Conceiva (Mezzmo Android) with the same results either way.