Print heads go to left grind

The carriage sensor (usually a photocell arrangement) that senses the carriage position when at the end probably has dirt or has failed. It usually is a couple of small black fingers that a "vane" on the carriage goes between. If the vane is broken or the sensor broken the carriage will keep trying to move farther as it cues up. Once it has cued up itself, it counts pulses to the drive motor to keep track of where it is.