Doug:
I think what has probably happened is over years of use the pivot hole in the sight blade has worn, but the base has not, because there is no movement of the pin in the base. When the pin was replaced it is tight in the base but the hole in the blade is still enlarged. I would drill out both the base and sight leaf to the next size larger pin. Use a drill that is about 1/2 a thousand under the pin size.
Probably the easiest fix is as Daryl suggested and punch the pivots with a center punch.
Bob