I struggled with this for days and nothing worked! I took a picture then the camera flipped itself to selfie mode...but selfie mode didn't even work. None of the menu buttons worked in selfie mode either ..it was just stuck there!
I opened Facebook and decided on a whim to try the Facebook camera. Not only did it work, but it unstuck the camera app!!!! So happy it's fixed, but frustrated I wasted so much time on ineffective "fixes"