I had a constant buzzing sound from the unit. I did what you recommended and could not stop it. Then I discovered that my handset also had the same buzzing sound so I unplugged the phone line and power cord (to the main phone unit) and it cleared up!
I've got a unit that is getting no sound to or from the earpiece at all, though the lifter still lifts when I hit the answer button. I'll try this reset before I order a replacement set.
I have the C053 model and have cleaned headset and base and can not get it to charge. I have noticed over the past few weeks that it will only stayed charged from 800 am to 100 pm. I have disconnected and restarted also. Any other suggestions?