They do go through lots of tests, including burn-in; they're also then shipped halfway around the world. We're aware of some badly made HDD cables which test fine in the factory, but fail in real life after some vibration; there's little we can do about it since EOL (ie, we can't shout at the suppliers, they won't take any notice) apart from fix players which show the fault. Our manufacturer changed supplier without us OKing the new part.
[email protected] are the people to talk to, but almost definitely you have a loose/bad hdd cable.
Hugo