After a reboot it’s always there, you just may not have noticed it before.
Our head end is constantly communicating with the hub having it adjust it's transmit levels and frequencies. When the modem first starts it's registration it scans the downstream to find the correct channel then increasing it's power level until the cmts replies to increase or lower it's transmit level to hit the receiver at the correct power. The increasing or decreasing it's power level until it hits the receiver at the correct level is ranging. As it’s adjusting power and error is logged if there is no response.
Think of it like two people shouting to each other over a large field. One person shouts a message until the other person says okay I’ve got that. At first the person shouting the message may not be heard and need to keep turning up the volume until he has been heard. Every time the volume is increased an error is logged.
Here to help! I'm an install manager helping out whilst working from home. Find out more