cant set part position inside of another part?

worked until it didn't ive gotten other parts to go in each other before but now it just wont work i turned their collision off and anchored it but it still wont work, i set the position like this but idk if its wrong or not.

whit.Position = Vector3.new(po1 + 30,po2,po3)
whit.hitB.Position = Vector3.new(po1 + 30,po2,po3)