Power save is malfunctioning?

When I close my DS lid to put it into power save, the game flickers in and out of powersave mode really fast and won't stop. It's akin to opening and shutting it super fast, it makes that little noise when the screens flash on.

Everything else is working perfectly, but this is a big issue for me because I play it in short spurts, so I need the power save feature. I have the original DS, one of the first models.