Oh dear! This is how the inside of a motor looks when it has not been serviced. Ball machines need servicing at least every two years, more so if its used at a tennis club. The grit and dirt gets into the motors and breaks down the oil and grease and then as you can see the motor stops working and will need to be replaced.
If you use your ball machine on artificial grass or clay then you will need to get your machine serviced more regularly. A full service with us allows us to re-grease the motors and oil the oscillation mechanism. Tennis ball machines are generally reliable but like a car they do need regular maintenance and it is much cheaper to service a machine than to replace the motors on it!