I can't find my camera Roll in my iPhone 6 plus and photo run to wrong folder

issue 1. my camera roll suddenly disappear from my album, I can view the new shot from "photo" but can't see the camera roll in the "Alums";

issue 2. I don't know when I have much more old photos show up in my phone and run to wrong folders, the title of folder doesn't match with the photo, all cat's photos run to my dog's folder, all goes wrong, impossible to find the photo when I need...

how can I fix this ?