If you can, take one of the split posts into Home Depot & speak with the store manager about it. He'll be able to assess if it's the method of installation causing the problem or if it's the material itself. If the S.M. is anything like ours, he/she will be honest with you. If it's the material, THD will make it right, so save what has been damaged already so they can exchange it out for you. It helps to have a receipt, but isn't absolutely required.
Oh...wait!! You said special order. It should be in the computer at the pro desk or service desk. No receipt should be needed. They can call it up in the system.