Sometimes it could be you may need to tighten screw on breaker. Maybe change receptacle and make sure all connections are tight. Make sure you are actually using a receptacle rated at 20 amps. Not the 15 amp that is common. The 20 amp should have a bit more surface area. These are the easiest and the cheapest places to check first. Make sure you turn power off before servicing breaker or receptacle. I work with a lot of refrigeration and equipment and this seems to be a problem a lot. May even change breaker. Depending on model, could have an internal problem like bad contact or what not. Would hate for you to have to change meter and not be the problem.