Tivo automatically downgrading signal quality?

New user here but have had our Tivo Premiere series 4 for almost 5 years. We have a Vizio HD tv that supports 1080i. We only use HDMI outputs and all our menus are set up for HD. We have never really had any issues but within the last few months, at least once a week (sometimes more) without fail the screen menus are pixelated and look like they're in 480p or less. The shows themselves don't look too bad, but you can definitely tell they're not displaying in 720/1080 anymore. This is true, even for Amazon video/Vudu video apps. The menus, screens, type is all pixelated. I have searched but cannot seem to find a way to refresh or get the Tivo to recognize that the video should be HD. The only solution, albeit extremely annoying, is to unplug the Tivo to get it to reboot. Then and only then do the menus return to crisp HD menus. Any help would be appreciated!!! Thanks