Rotary cathodes often produce deeper erosion grooves within one turnaround faster than the other. It has been observed that extra target erosion will consistently occur at one end of the target independent of the gas flow and magnet bar installation direction. This asymmetrical erosion takes place in cathodes operated in DC and AC power supply configurations. With the aid of plasma simulations, this phenomenon has been reproduced and a governing theory along with proposed solutions to this problem have been developed.