The Imaam made the Missed Takbeer in the second Rakaah while the Followers went into Ruku

Q: Salaah-559: The Imaam of the Eid salaah missed out one of the Takbeers in the first Rakaah when he folded his hands after the second rather than the third Takbeer. He therefore added a Takbeer to the second Rakaah so that he went into Ruku after the fifth Takbeer rather than the fourth. The followers however went into Ruku after the fourth Takbeer. Will they need to repeat the salaah?

Answer: If the Imaam joined the followers in the Ruku, there will be no need to repeat the salaah if Sajdah Sohu.' was made. However, if the Jamaa'ah was large and there was fear of confusion if the Sajdah Sahw was made. The Saidah Sohur will be waived and there will be no need to repeat the salaah either. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2