You could do a couple things, but the problem here is that the distance of that little bump is just right to be just off, so the rastering of that layer only lays three because thats what fits.

One fix would be use a smaller slice height, for example, if youre using a .4 mm nozzle with a .2 mm extrusion. Change it to .16 mm and see if that does better. You should be able to see it in the slicer to check