I would venture a guess and say that your bed is not perfectly level, and your nozzle is slightly too high from the build surface on the wavy side. Try adjusting your end-stops, or you can try adjusting your z-offset in your slicer software to lower the nozzle slightly and see if it goes away. Also, check your extruder motor, it isn't skipping steps by any chance is it?

The second photo is intriguing though with the spiral banding.. a setting in your slicer maybe? Do you have the vase mode enabled?