Tilting of the X-ray to the side or forwards toards the camera will adversely affect the score to some degree. There may even be uneven scoring in terms of right v left side and extra 3 or 4 points depending on the degree of lift. The effect will be largely on the first three items. Tilting is unlikely to effect the last six items to any degree.
Readers can differ slightly in interpretation.
The BVA use two readers from a panel of 9 or 10 selecting fairly randomly. Nevertheless even they can differ slightly in their interpretation of plates. These schemes also have appeal systems. Thus a dog that is anaesthetized MAY show a higher score for Norberg angle and Subluxation than the same dog would if merely sedated. Most schemes seek to anaesthetize dogs and thus all are being compared on valid terms.