The present invention pertains to a method for monitoring operation of a mining machine unit, particularly of a longwall mining system, having a shield unit connected to a material removing unit by means of an actuator for adjusting a distance between the shield unit and the material removing unit, the method comprises the steps of determining a position change of the shield unit during an actuating operation of the actuator; and a step of detecting a malfunction of the mining machine unit based on the determined position change.