The CRC on this lens is done with the rear, in my experience with lenses with rear CRC is that its really quite durable and stable. The front element is the one that can be off, I've replaced the front element on a couple of 24mm f/2's and they all needed fine tuning to the torque of the retaining ring holding the element in order to get max sharpness.
If its still a right/left issue it could also be the mount, check to make sure all the mount screws are set and torqued properly. Your camera mount could also be out as well.