Do prayers in which the word "wa-ala" was forgotten in the صيغة الصلاة الإبراهيمية (Ibrahimic prayer formula) become invalid, and must they be repeated?

An error in the Salawat al-Ibrahimiyyah (Ibrahimic prayer) does not invalidate the Salah because the ruling regarding the essentiality (rukn) of sending prayers upon the Prophet (peace be upon him) in the final tashahhud is a matter of scholarly disagreement. It is considered an act of recommendation (mustahabb) by the majority of scholars, while it is considered an essential pillar (rukn) by the Hanbalis and Shafi’is. However, those who consider it a pillar believe that the pillar is fulfilled by saying, "Allahumma salli 'ala Muhammad" (O Allah, send prayers upon Muhammad), and anything beyond that is supererogatory (mustahabb). Therefore, there is no need to repeat past prayers.