3421 Surface Texture: Roughness, Waviness, and Lay

[@mrugennaik534]

I am working on a project to measure surface finish on an aerospace part using a CMM. When the part comes from a forging vendor with 32Ra finish, I measure the surface finish on my machine using a program and I get good repeatability (10 samples) so I know my program and machine is good. the unwanted area gets machined and polished and then the whole part gets shot peened. I run the same program again to measure the surface finish (now 45Ra) part surface finish is within tolerance but this time my machine can't repeat the measurement in certain areas where it was repeating before peening. I will be grateful if you can shed some light on what I may be doing wrong here? Should I expect repeatability on a peened part? Also, how is the lay affected after polishing and peening?