Is it obligatory to repeat the prayer for one who missed bowing with the imam in the third or fourth rak'ah due to slow recitation or whispering during it, until the imam rose from bowing?

If a worshipper (ma'mum) is late in rising from bowing (ruku') because he was late in reciting Surat al-Fatiha, he should bow and catch up with the Imam, unless he fears that the Imam will rise from the last prostration (sujud) in that particular unit of prayer (rak'ah). If he fears this, then he must follow the Imam and invalidate that unit of prayer, performing a replacement unit after the Imam says the salutations (taslim). There is no difference between slow recitation and obsessive whispering (waswasah). The worshipper must follow his Imam immediately upon the Imam's performance of the pillar (rukn), based on the Prophet, peace and blessings be upon him, who said: "Indeed, the Imam is appointed to be followed. So when he says 'Allahu Akbar,' then say 'Allahu Akbar'; when he bows, then bow; and when he prostrates, then prostrate." It is obligatory to recite Surat al-Fatiha without a slowness that would hinder following the Imam, and to completely reject obsessive whispering.