Looks like I’ve finally encountered the failing battery in a cartridge video game. I decided to play “Zelda: Link’s Awakening” after many years. When I started it, I noticed there were no saves, and wondered. After playing for a couple hours (a good chunk of which was saving for a shovel and digging up most of a forest looking for a mushroom that wasn’t there), I decided to save and quit. After powering off, I figured I’d better check if the save worked. It did not. So, I guess I’ll have to play via emulator.