Kilk'dymga'qith laq Ik'vikvi
Ist the same problem as with any current TFT display. IIRC they are allowed to have something like 5 constant black or white pixels and 10 to 15 that are constant on one color or that cannot display one color. Up to that level it isn't considered a manufaturing error and you cannot return the TFT. You are right however that usually you won't have any errors at all.