I have intermittently had the battery drain issue since January and about 2wks after that started I started getting the camera issue too. It defaults to front facing with a 2 second timer set and I can't access the rear camera. I did an FDR after that but it didn't help.
I have discovered the safe boot fix doesn't work every time. It took multiple attempts of booting into safe mode, waiting a few hours , then rebooting. I use gsam to monitor battery usage. I haven't had the camera issue. Have you tried a new camera app?