When my ink cartridge carrier refused to move from the extreme right leftward, I saw there was something impeding progress. What it was, I couldn't discern. Had to start a tear down. Fortunately, I only needed to get to taking off the right plastic panel to understand the problem. A stabilizing arm on the extreme right rail somehow became dislodged. It was simply "hanging out". Tried several configs to see which seemed to be the best fit. The 2nd or 3rd trial-and-error worked. Within the arm were two small enmeshing gears. One of them meshed with one from which it was detached on the rail system. Ink cartridge tracked just fine afterwards. The plastic panel is just a snap on. Be cautious in prying loose with a flat tip each of the 2 snaps and you'll be fine.