The Sherrif Star hubs were a bad design, with the drilled outer ring left to sustain poorly-supported loading through the spoke's load path. The wide cutouts in the flange would seem to be the culprit here, not the metal.
The cracked upper knuckles was indeed common, which I attributed to the stresses of the bushing being pressed into the thinned (from the better model's finer finishing) upper knuckle. I actually replaced one of those knuckes once, and it was a pain having to concoct my own tooling/fixturing for the job of removing some of the pivot pins.
I'm willing to bet that
gfk velo is right on about the index springs inside of your shift lever being fatigued i.e. worn out.
That was my first guess, and he just gave you the part number!
Also slightly possible is that thickened grease is affecting the spring's holding power, and I am in the habit of routinely spraying some grease or at least lubricating oil into the greased ratcheting crevices of this style of shifter, to improve their snappiness.
