out of range or no power at base

Hi,

My VTech cordless phone at work has been acting up. The phone is fully charged and will work most of the time. Sometimes I'll dial a number, it'll ring, and it randomly shuts off. The screen will be blank for a couple seconds as if the battery has died. When it turns back on the display shows "out of range or no power at base". I am literally just 2 feet away from the base and the phone has been charging all night. As soon as place the phone on the base it'll work showing the battery is full, but when I take it off, it does it all over again.