If you look at the section on "alfaz al-jarh" in works on Usul al-Hadith, you'll find a list of all the words used to declare a narrator weak in hadith including "weak" (da'if/layyin), "nothing" (laysa bishay'), "not strong" (laysa bi qawiyy) etc. but "his book contains errors" is not amongst the words of jarh unless the errors are specifically in regards to the narration of hadiths. So your claim that al-Shafi'i said Muhammad is weak in hadith remains unverified and is no doubt a lie. Moreover, if you read the debate on Muhammad's book (al-Hujjah 'ala Ahl al-Madinah) in the book you mention Adab al-Shafi'i wa Manaqibuhu, which is downloadable here, the words you quote are not found. The debate can be found in two places, pages 81-2 and 123-6. In the second narration, al-Shafi'i mentions there are "errors" in your [i.e. Muhammad's] book, not that the whole book after bismillah is error, and then he lists a few fiqhi issues mentioned in Muhammad's book that he disagreed with. These are fiqhi differences of opinion, and in no way entail al-Shafi'i believed Muhammad was weak in hadith. Which I have shown to be false here but you repeat the same charges and claims even once they have been proven false. Al-Dhahabi's book al-Muntaqa is merely a summary of Ibn Taymiyya's book in which he made this claim, so he was quoting Ibn Taymiyya's view and was not stating his own view. Al-Dhahabi refers to al-Shafi'i as being from the students (ashab) of Muhammad in Siyar A'lam al-Nubala. I have mentioned repeatedly al-Nasa'i is a mutashaddid and his jarh is not always accepted, so it will not be accepted in the face of the ta'dil of Ibn al-Madini and al-Daraqutni mentioned in the first post. Why do you not answer the most important question asked: On what basis, and based on which accepted principles of al-jarh wa l-ta'dil, do you favour and give precedence to the jarh on Imam Muhammad over the ta'dil?