Checking in varnish doesn't happen solely in the finishing process. It can happen from direct exposure to sunlight after a period of cold temperature, changes in humidity, i.e. too little or too much water in the wood. Think of it this way- wood contracts and expands and varnish is hard. Varnish can only expand so much (flex) until it cracks (it is rigid like glass). You can call them, and maybe they can set you a new stock set, but it could happen again. This is one reason I prefer oil finishes or varnish finishes.
Edit: Think about this. Your rifle gets on a plane in Goodyear, AZ where the temp is ~75F. Then, in flight, the cargo hold temp gets to about ~30F. Then the plane lands in KY, where you are, and sits in the sun while being offloaded for 45 minutes. Then your rifle is sitting in an oven for 45 minutes! (enclosed metal cargo hold with sun beating on it) Just an idea.