Knowing I could get a replacement, I went ahead and tried to salvage this one.
As I suspected, the soft brass rectangular key had worn down and was very not fitting the lever well.
I just ground off the head, made a jig in a 2x4 to hold the shaft with the drill press.
Tapped a small thread and with the use of a very small screw and lock washer seems like all of the play is now out of the shaft.
Just need to add a drop of lock tight.