Ignition lock assembly

[dmjlambert]

My observations
I think I'm showing the incorrect orientation of the pin in the first 2 pictures, because when inserted this way the pin pushes down but it sticks in the down position. In pictures 3 and 4 I inserted it the other way and it presses in and springs up. I don't know for fact the orientation because after I removed the cylinder I touched the pin and it popped out and onto the floor of the truck.
Cylinder keeper 6 appears to keep the cylinder in the assembly in all normal positions of the key. Push the pin through the pin release hole 4 in order for the pin to clear the pin block 5 to move the cylinder keeper 6 into the cylinder keeper slot 1 and that allows the cylinder to release and come out of the assembly.
I have noticed the latch 3 is depressed when the key is inserted, and the latch sticks out when the key is removed. The key can only be removed if the latch is not being held in. So areas in the assembly that are the latch up positions 7 are places where the latch is free to move up and therefore those should be where the key can be removed.
The spring cover 2 does not move, it is swaged into place.

So here is my problem. When I put the cylinder back in the assembly and it snaps into place, I can depress the pin through the hole and turn the key to the right and it moves through the off, on, and start positions. In the start position the key will tend to spring back to the on position. All good so far. If I turn the key to the left past the off position, it sticks in that position forever, unless I depress the pin through the hole again. Then I can turn the key to the right back to the off position. I can remove the key in any position. The whole assembly worn out, or just the cylinder, or something else wrong?