The barrel bearing can be difficult to re-install in the axle tube. It tends to rotate out-of-square during installation. Gently tap the axle, and closely watch the bearing. When it gets out of square, use a flat drift through the hole in the axle hub to tap and adjust the bearing square again. Repeat as needed until the bearing gets far enough in to stay square. Your adjustments with the drift, actually happen on the backing plate, which in turn moves the bearing back to square.