Sure it's the grinder? You've had good v60 brews with your recipes and you've ruled out water? If your not 100% sure and don't have another grinder to compare to, I'd have a good local roaster grind a bag for you on their high end grinder and buy an identical bag of beans to compare it to with Op2.

That grinder does have a reputation for being lackluster for pour over, but I'm not sure that's your issue.