well, if it's only "most other channels" I think you need to check the aiming of the dish. Before loosening anything, just push on the dish(not too hard) one way or the other(watching Q meter on a TP that registers), to get a grasp of the direction it's got to be moved. Then check 11929 v22.000 Q.
BTW, is this a fixed dish, or on a motor? If on a motor, maybe just moving it (sat position) a tenth of a degree, or 2, E or W?