Why do I sometimes find different opinions for the same school of thought in Al-Jaziri's book "Al-Fiqh 'ala al-Madhahib al-Arba'a" compared to other books?

There is no surprise in the divergence of madhhabs (schools of thought) due to the differing evidence or methods of deriving evidence, while all of them rely on the Qur’an and Sunnah or the rules extracted from them. This also applies to the divergence of opinions within a single madhhab, such as the existence of different opinions from Ibn al-Qasim and Sahnun among the Malikis, and from Abu Yusuf and Muhammad ibn al-Hasan among the Hanafis, and the divergence of opinions in books such as Al-Umm and Al-Majmu' for the Shafi'is, or Al-Furu' and Kashf al-Qina' for the Hanbalis. It is natural for a particular opinion to be favored by one author and another opinion to be favored by another author, and this does not invalidate the authenticity of either book.