Help needed for quick-acting compound on Hardinge HLV (not HLV-H)

As long as I've had it, the compound on my HLV has been a problem--it retracts OK but the dial becomes loose and you lose your position. I finally decided to attack it--something has to be broken or askew.

I found a broken bit sticking out of a hole in a part that I think is the Sleeve Key (#9548 in the Parts List, attached). I think that this broken bit must have come from the Guide Screw (#L-9551), which is a 1/4-28 setscrew that I'm guessing was turned down at the end to fit in the hole in the Sleeve Key.

The attached photo shows the Sleeve Key, the broken bit, and the Guide Screw. You can also see the place where the Sleeve Key goes, if I am reading the parts list diagram right.

I am hoping that someone who knows this assembly can verify or correct my thinking.

From memory, I think you've got it right and are reading the parts correctly. Looks like the tip of L-9551 is broken off. It's an easy part to make.

But while you have the compound apart, I recommend that you disassemble further and look at the helical groove and key that directly operate the quick-retract feature. I recently repaired two of these compounds that had badly worn helical keys and significant wear to the helical tapered groove. I milled out a new helical slot and made new longer bronze keys to fit. The process is described in this photo album.
https://groups.io/g/hardinge-lathe/album?id=83720

In my case, the straight slot, key and guide screw that are the subject of your post were in good shape.

Jim