SHAFAQNA – The Grand Ayatollah Fayyaz answered a question about performing Salaat in Mosque and doubting the justice of the congregational prayer leader.
Question: If in a place where the congregational prayer is held, because we are in a hurry, or we doubt the justice or correct pronunciation of the prayer leader, if we perform Salaat individually, is this individual Salaat void (Baatel)?
The Grand Ayatollah Fayyaz: If it causes the defamation of the character (if it causes disrespect) of the prayer leader, yes it is void; and if it does not cause the disrespect of the prayer leader, it is not void.
Source: PERSIAN SHAFAQNA