try warming it gently -- my XL would get tight and hard to focus -- and hard to mount/remove lenses -- when it got cold because the focusing collar is a plastic that shrinks when it is cold. When I took it camping and it was near freezing the damn thing was impossible. That plastic also shrinks with age, so being hard to focus is a very common problem with these.
A coupla minutes with a hair drier won't hurt it, might help. Then remove the lens and, with some fine sandpaper, sand the inside of the focusing right BUT NOT THOSE TABS LEAVE THE TABS ALONE the ones that fit into the groves on the lens barrell.
sanding the inside of the ring will loosen it up. Hold the camera upside down so the grit doesn't fall into the camera. Be gentle, always gentle.