What are the situations in which one must go against the Imam?

If the Imam stands for an extra rak'ah, or omits a pillar such as prostration, or clears his throat in a way that changes the meaning, or makes a melodic error in Al-Fatihah that alters its meaning, or if following him leads to the disruption of a pillar of prayer such as tranquility (ṭumaʾnīnah), then it is obligatory to leave him and complete the prayer individually; otherwise, the prayer of the follower becomes invalid. If a person joins an Imam who is praying standing during the last tashahhud, it is not permissible to follow him. He may leave him by intention and make the salutation, or wait for him and prolong his supplication until he makes the salutation with him.