I guess my question would be...how tight does the hub fit on the shaft. As I think about it, the collar on my Clausing Kondia pulls out sometimes when I am repositioning the handle. I always tell myself that I need to look into that when it happens, but I'm in the middle of milling something and then I forget about it.Yes the hub is keyed to the shaft. the lever slides on the hub. You are correct. The issue is that the hub is not held onto the shaft. It will simply slide on and off of the shaft, if the key is aligned of course.
There is a grove cut as can be seen for a C-clip to hold the lever onto the hub. I have removed the C-clip as I attempt to cipher this issue out. It has no bearing on the hub to shaft connection.
Not sure if you figured out your hub situation but I have that exact mill. I pulled the hub off to take a look and there is nothing holding it on its just a "tap fit" with a rubber mallet. There are 2 small threaded holes on the hub flange that I used with a couple of screws to remove the hub.