Yeah....that's not what I do.I'm an ACTUAL DJ. Tables and all. I'm a WYSHIWYG (What You See/Hear Is What You Get) DJ. I do everything live. If I have a pre-recorded mix, it's mostly for show and auditions.
This is the SAME shit with GB/GBA games. I HATE doing this shit. I have the original Pokemon Games, and it's a bitch trying to change those cartridge batteries without fucking the tabs up.
My best guess for you:
The save battery inside the cartridge has most likely died, or is close to it. There is a small cell battery inside the cartridge which powers the memory for saves and the like. Over time, it loses its charge and, and your game won't save/saves disappear. You can replace the battery yourself, if you know what you're doing, and have the tools. I recommend going to the iFixit YouTube page and searching for the project. You can probably just do a general Google search for it and find it.