How much leeway would make a difference on a post?

I bought a controltech post and it’s slipping. Got some verniers to measure it against the old one. The new one seems to be around 31.5 to 31.65 – seems vary a bit each time I measure. Old one seems to be nearer the 31.6 in most measurements. Is this enough to make it slip? Can I return it or will they say it’s within tolerance?