Why are you asking me who you should sue? A “defect” can be anything in reality, but typically a design error which means something is not performing correctly although at the time of sale appears to be and potentially a while longer. I participated in a rather abstract claim against a manufacturer who made a distributor (for injection of chemicals) for seawater, it worked fine throughout the warranty period and then catastrophically failed because they had supplied it in the wrong material and the chemical had been corroding it away slowly. So it didn’t fail from manufacturing, e.g. a poor weld etc, but a latent defect, i.e. an engineer had specified an unsuitable metal, that a layman / customer may not have understood or appreciated as they were relying on the expertise of the manufacturer.
Likewise you general pc buyer expects Apple to be an expert in designing a computer so would not identify or appreciate a design flaw in a screen cable that was designed too short. It doesn't matter if Apples flaw was an error by accident or intentional (e.g. cost saving / inadequate safety margin), the flaw was there at the time of sale.
