Do you mean the lines created when you clean. The head is round, the top pushes fibers right and the back pushes fibers left. If that's what your talking about then you need to groom.
If you mean it's cleaning uneven and leaving a line it's because it's a single disk. It's almost impossible to keep that head flat on the carpet. It's the same with a 175, rdm, or rx. A single head design is flawed from the go, one side or another is going to be digging in while the other side is lifted. That makes the original rv, the cimex, and some op machines clean better. If you can keep the head flat on a single disk you will be cleaning better but working harder. The machine will fight you as it tries to go every direction at once.