With no load on the servo, it should be drawing about 7 to 12 milliamperes at rest. As soon as a command to move it occurs, the current will jump to a higher value. How high? depends on the load but can easily approach 1 ampere for a fraction of a second. Now if the servo is stalled (movement blocked in some manner) or a very high amount of friction, this high current can persist until the load is removed or the brushes burn out or an electrical component fails due to overstress or heat. It may help you to dissconnect all servos from the receiver and then connect just one at a time while monitoring the current. When you find the sero(s) that cause the high current draw, you can further trouble shoot to see why that is happening.