Strange 3ds behavior..

For some reason my 3ds xl /LL screens keep turning black randomly I don’t know why it does this whenever it does this from what I see in the light the system thinks the lid is being closed because the light slightly dims when you close it and it does this randomly whenever I’m playing on it! It’s strange and for anyone wondering this 3ds is one that used to be Japanese that I changed the region to English and modded it and the sd card is completely compatible with it too so I don’t really know what the problem is and I have a second 3ds that does the same however that one is a normal American one if anyone knows how to fix this issue than please don’t hesitate to leave a comment