I’ve found that part of the problem can be the top surface pattern. As some suggested, it might be laying down some lines in one area, working in another area, then coming back to the first after it’s cooled. Look at the printing pattern of the top layer by inspecting where the nozzle is moving in the slicer. Playing around with patterns like aligned rectilinear instead of rectilinear (IIRC) can make a big difference.