Hardware "bricked" 3DS booted to HOME Menu, ONCE

[Halvorsen]

We have a 3DS I assume is on original firmware <8.1.
It was bricked for apparently no reason. Recovery mode does not boot up, HOME Menu Management (L/R/UP/X) doesn't boot up either.
Yesterday, it boot up to the Menu but turned off afterwards. Normally, I'd think that this has something to do with the ribbon cables for the screens. However, both screens have the backlight on and just hangs at a black screen. If it was a cable failure, the system would immediately shut itself off upon pressing POWER.
It's weird. No SD Card or games inserted. Disassembled and everything lookd okay. But it can't be a full brick, it just booted up not long ago. Any other tips? This was never hacked btw.

 

[dg_dex]

Any signs of a hard moded ever been installed? That sounds like a hardware fault. It could even be a corrupted nand image.