I'm puzzled about the non-repeatability issue being addressed by trimming the jaws..
It just seems like assigning fault to the part that is not guilty.
The comment that the original jaws were cracked or broken tells much.
Also, For small work, just pull every other jaw and use the device as a three jaw.
For myself, A 6 jaw is ONLY useful for holding thin pipe or tube , rings etc. And not nearly as good as machinable pie jaws. I had one once, Sold it, Never to be regretted.
I'm surprised that the technique of Lapping the jaw contact surfaces hasn't been mentioned.
A solid piece, turned to suit. A dead center in the spindle, and solid center in the. tailstock.
Charge the lap, and hold it by hand. Tighten the jaws down "just enough" to rub.