Could you please help me with identifying what’s going on?

Hey, everyone! Could you please help me with an issue with my 3DS? What could it be? I was playing it at bright level 1 but then I noticed a quick change to bright level 5, then it went back to level 1. When I finished playing and folded the lid, it shut down. I turned it on again, went to the options and as soon as I touched level 3 bright, it shut down again. Now simply folding it makes it shut down. The battery is still the original one, I've had this 3DS since 2021, it never had any issues. Starting it again after it shuts down like that keeps the previous wallpaper (it only changes if I turn it off properly).

I appreciate any guidance!