If the Imaam Forgets to Sit for the First Qa'dah

Q: Salaah-467: Zaid was leading the Witr salaah during Ramadhaan when he forgot to sit for the first Qa'dah and stood up for the third Rakaah. When the Muqtadis corrected him, he returned to the sitting posture. Will Sajdah Sahw now render the salaah valid since he returned from a Fardh (obligatory) posture to return to a Waajib (compulsory) posture? If not, why not? You have stated in a previous Fatwa that the salaah will be valid because the Imaam returned to the sitting posture to make amends and not to return from a Fardh (obligatory) act to a Waajib (compulsory) act. The Urdu translation of Fataawaa Aalamgeeri (Vol.1 Pg.15) however states that the salaah will be invalid according to Imaam Abu Haneefah RAH. and it is this opinion that is preferred Please explain the discrepancy.

Answer: There is a difference of opinion on the matter, the preferred opinion being that the salaah will not be nullified even though the act is wrong. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2