A picture would help as would knowing what you are cutting. Soft woods can telegraph impact marks from almost any machine where harder materials do not. The point is to make sure you are not trying to fix something that is not the machine's fault ;-) since you say the length of your board I will guess the lines are running length-wise for the whole board, not cross-wise for the whole board but, this may not be correct.
Here is an example of a knifed machine surface and a spiral machine surface:
Attachment 379756
In this case I would say the cuts on both were made by cutters needing attention. When I see trails like the ones in the lower picture it is time to rotate my inserts. Do not confuse this with the scalloping that is inherent in how planers operate. There is no way to pass a cutter through a material in an arc (like the cutting edge on a round cutterhead travels) and leave a flat surface. It is "really flat" and "smooth as a baby's butt flat" but, in the right conditions the arcing cut will show.
Unless you are doing rough-work, no surface goes from machine to finish but, we would like the surface to be as nice as possible. Again, a picture would help but, if a new cutterhead is leaving marks like the bottom pic, something is incorrect. I know Byrd had an issue years back where the index cutters were not getting seated correctly at the factory resulting in a variety of behaviors. I guess I should stop talking till we see a picture of exactly what we are trying to diagnose.