Flashforge creator pro 2 with PLA, standard quality preset, textured removable magnetic bed on the build plate.
The first lines are straight, but as it makes more parallel lines to build the layer, it starts to develop a scalloped pattern. This creates issues with smoothness when it fills back to join it from the other side later. I’ve leveled the build plate, although I suspect it’s not perfectly flat and maybe slightly higher in the middle. Is this my problem? It appears to have the pattern even away from the middle if that makes sense.
This is my favorite guide to start with, it’s not necessarily specific to Simplify3d: https://www.simplify3d.com/resources/print-quality-troubleshooting/
Your picture looks kinda like the over-extrusion picture to me.
I have also found the orca calibration guide helpful even if not using Orca because it has some explanatory photos: https://github.com/SoftFever/OrcaSlicer/wiki/Calibration