Return it for repair. Nothing you can do yourself on it.
My first guess is a variance of front receiver ring diameter. A bit taller and/or wider on the second rifle.
I would try the non adjustable set up on an other rifle.
Could the zero stop be limiting your elevation?
Is the error large or small?
There’s no side focus on the 3-12 PMII if I recall — do you know from the literature what the factory parallax distance is? My guess is it’s likely 200 or 300m.
If the error is small I wonder if it’s a parallax problem, that arises from using 12X to zero the scope at 100 yds?
Maybe try again using lower magnification — say 6X — and see what happens.
Well done .
Problem solved.
..thanks a lot