Thank you for your reply @sa2000 and your investigation. I have to say that this is surprising as this was the cause of the first report as well.
How is the simple playback of mp4 files on a streaming device causing such extreme memory consumption? It seems like such a fundamental feature for what the streaming device is built for that this should never happen. This is like a car tire going flat after exposure to the tarmac for a few minutes. 
I can tell you that we have also been using YouTube to watch many hours of live-streaming NFL Sunday Ticket on all three of our Rokus and it has never crashed on any of them.
I hope you can understand the concern/surprise here.
