To what extent are Al-Bayhaqi's hadiths authentic?

Imam al-Bayhaqi (d. 458 AH), one of the leading Shafi'i hadith (definition) scholars, was renowned for the abundance of his narrations and writings, such as "Al-Sunan al-Kubra" and "Shu'ab al-Iman." These works were characterized by high quality, combining the sciences of hadith and fiqh with an exposition of the defects (ilal) of hadiths.

His condition in his writings was to limit himself to the authentic (sahih (definition)) or to distinguish between the authentic and the inauthentic. Scholars like Ibn Taymiyyah praised him for his ability to differentiate between the sound and the unsound.

Despite the prevalence of authentic (sahih) and good (hasan (definition)) hadiths in his works, they also contain weak (da'if) and fabricated (mawdu') hadiths, and he may sometimes not point out their weakness, or he may authenticate something that contains weakness or a defect. Thus, the scholarly value of his authentications is below that of the authentications of the critical imams.