Been meaning to report this for a while, so I don't think it's a new bug, but seems easily reproducible. When I open the iOS app to the guide while connected to wifi (remotely), but then walk to where I drop off wifi and am on cellular, the guide info disappears. I haven't found a way to get it to repopulate outside of force quitting the app.
I just released a new iOS and tvOS beta that should resolve these issues that you're seeing.
Please check it out and see if it improves the situation for you.
That definitely fixed the issue going from wifi to cell, and even back again. Nice work.