Phillips cd pro 2 center hub has cracked 2 times on my Audioresearch CD 9 Cd player

I've owned this player for less than 6 months and have cracked the plastic centering hub twice so far. Though it's an easy fix does any have any ideas why this might be happening?
When I place the disc over the hub the disc isn't laying flat on the turntable I have to snap it down over the hub. I'm sure this force has caused the hub to crack.
is it normal to have to do this?
Mike