Have you tried clearing the app data too? If not, please head into Settings > Apps > Camera > Clear data. This won't delete any pictures you have taken. Once you've done this, please restart your phone.
If you're still experiencing an issue with the camera focus, please send an Error Report via our Members App so we can a better understanding of the issue. To do this, head into Samsung Members > Get help > Error reports > Camera > Pop in all the information. Once you send this off, our engineers can get a closer look, and they'll be able to provide more information.
Exactly same issue, started in the last approx 1 month. A small shake of the camera/phone seems to clear up the focus issue (to me indicating a hardware fault with that lens) until the next time the camera app is opened.