Bukhari and all the hadith book are attributed to the person who compiled them. You must remember that in 8th century, communications and travels takes weeks. The arabs are scattered all over and when Bukhari meets one who says he heard it from so and so that the prophet said...he wrote it down and collected them all.Why do you consider the bukhari hadiths that bro @JohnTan quoted you as unauthenticate but other parts of the same hadiths by the same person as authenticate?
https://sunnah.com/bukhari
Thus just like the bible people try to corrupt the religion by attributing fake hadith.
It is almost impossible Bukhari could verify every single one of those as authentic.
So the exercise to ascertain authenticity is left to the later generations.
Remember hadith is not one long continuous narrations, but rather short sayings and actions as witnessed by those around him. Most are true, others fake.
The amazing this about Bukhari is that he memorizes 100,000(?) word for word. And at the end of his life he compiled it into a book.