Either the head is dragging on something with ink on it, ink is built up on the bottom of the head, or the head may be damaged internally. I would check the bottom of the head first to make sure you don't have a ton of ink building up which makes little inkcicles that can drag on the media but also contaminate your nozzles. Also, with the power off, manually move the head back and forth and see if the head is slightly brushing up against the flushing pad to the left of the capping station. The sponge can well up if it's older and touch the head.