Dropping back to the main Roku screen is a different problem than what I had as I could get successfully logged in to PureFlix, I just had to enter the log in data every time I wanted to watch something. Pureflix eventually got that resolved as the channel now stays logged in on my roku devices. As it seems that you have one roku device that works and another that doesn't you might want to try the steps of deleting the pureflix channel and reinstalling on the problem device.
