How is Imam Al-Bukhari's inclusion of narrations from Humran ibn Aban in his Sahih correct, despite his weakening of him?

Imam al-Bukhari, in his Sahih, deals with narrators about whom there is criticism using the methodology of "selecting from the hadith of the weak." He only transmits what is sound from their narrations, for not everyone who has been criticized has all of their narrations rejected. The weakening may be specific to a situation, a shaykh, a country, or a particular hadith.

Al-Bukhari transmits from these narrators for several reasons: 1. That the correct view is their authentication, and their weakening is rejected. 2. That the narrator's weakness lies in his singularity, so he transmits from him what agrees with reliable narrators. 3. That the narrator's weakness is specific to his narration from a particular shaykh, so he avoids narrating from him. 4. That the narrator is weak due to اختلاط (confusion/memory loss), so he narrates from him what he heard before his اختلاط. 5. That Al-Bukhari did not include an original hadith from him, but rather in supporting narrations (متابعات), corroborating narrations (شواهد), or suspended narrations (أحاديث معلقة).

Therefore, the presence of criticized narrators in Sahih al-Bukhari is not an objection, because Al-Bukhari selects from their hadith what he is certain is sound. This does not necessarily mean an absolute authentication of the narrator, but rather it may be an authentication for a part of his narrations or for a specific purpose, such as supporting narrations. An example of this is Humran ibn Aban, from whom Al-Bukhari transmitted only two hadiths, both of which are acceptable and sound.