Does not severing the trachea when slaughtering birds affect the permissibility of eating the slaughtered animal, and does the ruling differ if the slaughtrer is unaware of that?

If, during the slaughtering (dhakāh), the two jugular veins and the esophagus are severed, then the slaughtered animal is permissible to eat. The most complete method is to sever all four vessels (the esophagus, the windpipe, and the two jugular veins), but it is sufficient to sever three of them.