Yo, i am experiencing almost the same , but with me the photo camera wont start immediately , only if i switch to slowmo video mode and than back to video and photo , than it all of sudden works , if i switch back to photo from the video modus the photo still dont work only with if i switch to slowmo and back , and i only can select my front cam if i do everything in that order , i found this very annoying , and all this happened after a screen replacement that i did for like a week ago , I also tried hard resetting the phone , multiple times , tried pressing the camera and everything , with no succes, i tried the reset with DFU mode and also with just iTunes , all methods and still the same plus i forgot to add that i always had the phone set up as a new phone and than afterwards tried to restore the backup but even before i had restored the phone the camera problem was just the same ! stupid 5s screen replacement :(