We have a Walter Heltronic MiniPower. The machine is about 15 years old. We have started to hear the Y-axis making noise in rapid travel. We are uncertain if is the servo, or the motor or something else. There is a oil reservoir that feeds the ways. This does not seem to be emptying at the same rate that it used to. We don't know if this connected with the noise we have been hearing. Has anyone else had an issue like this?---Thanks