Is it permissible to pray behind people who are innovators (mubtadi'un), even if the Imam has been warned about their innovations?

Innovations (bid‘ah) vary in their severity. Some lead one out of Islam, while others do not. Some pertain to creed, while others relate to practical branches of the religion. The role of the Imam extends beyond leading people in prayer to include inviting them to Islam, teaching them, and advising them. He should benefit from the mistakes made by the congregants, transforming them into material for da‘wah (preaching), just as the Prophet, peace and blessings be upon him, did. The Imam must invite [to Islam] with that which is best, using various methods such as reciting and explaining Qur’anic verses, inviting scholars to deliver lessons, distributing pamphlets, or creating an audio library, while being characterized by wisdom, knowledge, and sincerity. The caller [to Islam] must clarify the errors of innovations and doctrines that contravene the Sacred Law, and invite people to refer everything that is unclear to them to the Qur’an and Sunnah. Whatever agrees with them is the truth, and whatever contradicts them must be abandoned.