I would take the corrector off very carefully and inspect the baffle tube to see if there is enough lube on it or maybe its completely dried out. When you remove the corrector be sure to notice any alignment marks so that you get it put back together properly. Mine has a red mark on the glass corrector and a red mark on the rim of the tube. If the baffle tube is completely dried out I would think you could add a little lube to it. Just be careful not to get any on your mirror. A little lube will go along ways. Then you will have to run the focus all the way to the left side until it stops and then all the way to right side until it stops so that the grease gets distributed evenly. Or perhaps something is binding in the focuser itself? Is the focuser shaft bent perhaps or maybe something is binding inside there? Also, you could ask uncle Rod on the SCT forums what he thinks. He has lots of experience with SCT's. Hope you get it fixed.