I am still able to reproduce your original failure 100% of the time on every device I have (Firestick Max, Shield, Chromecast Google TV, Sony Google TV, Samsung Android phone). Only one channel of the guide is blank after looking ahead a few hours and only after that channel was played then the app backed out and resumed. If the app does a new launch, the problem never shows up until it has been resumed.
I also can always duplicate this failure. If I hold down the right movement key, the guide will eventually freeze up. No selected entry shows on the screen and I press the back key to reset the guide. Pressing the key at slow enough intervals may keep it from freezing up.
I have a Windows 11 Pro server wired to my router, and the Shield is wired to the router. My other clients only use wifi. They all have these same problems.
The developers have not been able to duplicate the failures. I haven't found a setting or condition where it doesn't fail. Not sure how to troubleshoot any further. I don't use the guide much because it is a pain to move several days ahead.