AIUI, the systems are designed to reset to a known good "standby" state if they don't receive any commands after some time. Of course the recovery routine itself can't be guaranteed, especially when the hardware itself is wonky, but suffice to say the updates aren't completely rawdogging it every time. There's an overview of how it works at https://voyager.jpl.nasa.gov/mission/science/thirty-year-pla...