We are users of AKM73 seriese motors. They have been in use over more than 2 years of continuous operation. we are using servostar S712 drives. System was working properly for 2 years but recently we are facing problems such F08 (Overspeed), F25 (Commutation Errors) , Noise from motor etc etc. We read in the motor manual that bearing needs to be replace after 20000 hours of operation. are these problems related to the bearing of motor? Can we relate increase in problems to the motor bearing? How we can check the healthiness of motor bearing?