Why when shooting in portrait orientation the camera shoots normally, and when landscape – blurry?
Most likely in the “defocus” of the camera when changing the orientation of the display is due to mechanical failure. To verify this, lock the screen orientation in the Control Panel and change the position of the smartphone from vertical to horizontal during shooting.
Check the operation of auto focus in different shooting modes.
If the loss of focus does not occur or it will manifest itself only in some modes, a software problem, you should restore the firmware via iTunes on the computer. Most likely, the loss of focus will be repeated, which would indicate a breakdown in the smartphone.
Independently solve the problem will not work. The point is either in the garbage got into the body, or in the camera unit itself. In the first case, opening the iPhone and banal cleaning will be enough. In the second, which is unlikely, repair or replacement of the camera.
By itself, the camera or protective glass moves extremely rarely, because inside the case all elements are securely pressed to each other. The offset could manifest itself in any orientation of the apparatus.
Most factors indicate the presence of debris inside the enclosure. In no case should not try to independently blow it out of the apparatus. This can lead to serious damage.