My Pokémon game keeps auto-resetting

I was playing Pokemon Sapphire, and I encountered a glitch of some sort. While I was in the middle of a Pokemon battle, my GBA SP decided to randomly automatically restart.

At first, I thought it may have been due to an old system, however it continued repeatedly. I switched the game into a DS Lite, and that did not fix anything.

I was able to figure out that the auto-reset only occurred when I switched out to specific Pokemon, Gardevoir for example. Has anybody else encountered this issue?

There may be some sort of glitch in the cartridge or the Gardevoir. In one of my games, Pokemon Platinum, which I bought new, the screen would make a little black streak when using an HM move. even after restarting the game, this would still happen.

I would recommend trading all of your Pokemon to another game and restarting Sapphire. See if Gardevoir affects your other games if you do this.

I have never ran into this issue. It may also be the internal battery, but I cannot be positive. These are all suggestions, so I cannot guarantee they will work. Good luck and be sure to catch 'em all!