Quote:

""I can see a very narrow moon shape of light coming from the other side.""

From this, it sounds like the roll pin broke and one of the pins came out and the other might still be in there but not all the way into the cavity.



A moon shaped slice of light would lead me more to believe it's a cone type and the thrust block is sitting low .

Is the light you see in the very middle and maybe like it's coming thru a 1/4 hole ?

But as dogdays said , just pull the chuck and fix it ... unless it's a cone type then it's going to require you to disassemble the chuck and that might be above your pay grade ?