Recently i had conducted SPC study for some pressing component having the critical dimension of 17 mm with -0.2mm tolerance. I had used recently calibrated 0.01mm L.C digital vernier caliper . And collected 10 Subgroup and total component used is 50. The result was CpK=1.42 & CP=1.69. As per my company norms the above mentioned result is in Green Zone but the study has been failed in A-D test and the Pvalue is 0.0069 . I don't know what action i have to take to get the result OK & what are the root causes behind the failures? Please help me.