Ok, it doesn't appear that the issue is that version of the App vs Android M, because it still runs fine on my Nexus 6. It has to be something specific to the Nexus Player / AndroidTV. I went ahead and grabbed the latest version and modified it, but I am at work and don't have a nexus player here to test on. Additionally, even at home I do not plan on running M on my players, until Football season is over, Sorry. Feel free to give it a shot and let me know if it works at all. This has the x86 folder removed, and the Default Page patched to live.
Edit: Removed Download as we verified it does not resolve the issue. Additional Information on this, it appears Comcast is aware that this app has the same issue on quite a few devices. The Media Player that comcast uses is not their own, they use the upLynk player. It appears that Comcast has been waiting on an updated version of the player, for quite some time, that improves compatibility with android devices. All of which exhibit the same behavior we see. Will this fix the issue for certain? quite possibly not, but besides rolling back to 5.1.1, it appears to be the only hope we have.