I've been wrestling with this problem with my CR-10S with an e3d v6 hotend for quite a while now. The layering is quite inconsistent in the X and Y directions (and appears to be about the same in both).
I've gone through the hardware with a fine-toothed comb, and I am confident my belts are tight, axes are secure, and bolts are snug. I'm less sure about settings.
I've been having a strange problem with my Creality CR-10s. I'm getting these areas on the sides of my prints which stick out or are too far in and appear to be where the geometry changes on the part. I'm using Esun Black PLA with the z-seam fixed the the edge where the problems are being seen. I've tried changing the location of the seam, and the issues are seen on other areas of the part.
My CR-10S (dual leadscrews) just arrived, but I have run into a problem. After the first layer, which usually looks perfect, the layers look over-extruded and ugly. I read an earlier thread about this problem with a regular CR-10, and the solution was to loosen the roller opposite the z-axis stepper.