Is it permissible to repeat the obligatory prayer individually after performing it in congregation due to the imam's haste?

If the Imam's speed does not disturb tranquility (ṭumaʾnīnah), then the prayer is valid and does not need to be repeated, due to the Prophet's (peace be upon him) prohibition of repeating a prayer twice in one day. However, if his speed does disturb tranquility, then the prayer is invalid and must be repeated by both the Imam and the congregants. Prayer is not repeated for lacking khushu' (devotion). The Imam should be advised gently, as he is entrusted with enabling the worshippers to perform the obligatory and recommended acts in prayer.