I don't know if you got this figured out or not but I took another look at your pics and the fork looks short or something. Is it the correct fork?

If it is too short or if it travels too far, it looks like the arc it travels could possibly cause the clips to walk off the end of the fork. I don't know how better to explain it.

If you still have it off the truck, cycle the fork as far as it can move and see if the clips are forced to travel off the end of the fork. Just another possibility.

I have a W56 I just pulled from my truck I can look at tomorrow if you haven't figured anything out yet.