Does repeating the Takbir out of forgetfulness after saying "Astaghfirullah" cause one to miss the attainment of the first Takbir mentioned in the Hadith: "Whoever prays to Allah for forty days in congregation, reaching the first Takbir, will be granted two absolutions: absolution from Hellfire and absolution from hypocrisy"?

Saying "Astaghfirullah" (I seek forgiveness from Allah) inadvertently does not invalidate the prayer nor justify repeating the opening 'takbir' (Takbirat al-Ihram). If the worshipper repeats the opening 'takbir' without nullifying the intention of prayer, then their first 'takbir' is valid, and they have caught the opening 'takbir' with the Imam. However, if they nullified the intention of prayer, believing it to be invalid, and then made the opening 'takbir', they would have made the opening 'takbir' after the Imam, and thus missed the opening 'takbir' with him.