Is it permissible for the Imam to issue a fatwa from the minbar that the prayer of one who prays Tarawih eleven rak'ahs is invalid, and is praying Tarawih at home in the last third of the night better?

It is not permissible to say that performing Tarawih prayer with eleven rak'ahs is impermissible, for the Prophet, peace and blessings be upon him, did not exceed this number, neither in Ramadan nor at other times. Scholars have unanimously agreed that there is no obligation to limit the number of Tarawih rak'ahs; rather, they differed regarding what is superior. Ibn Taymiyyah said: "Whoever thinks that the night prayer of Ramadan must be eleven rak'ahs and no more, has erred." The Imam should fear Allah and not be fanatical. It is permissible for a Muslim to perform Tarawih prayer in his home if he does not feel comfortable praying behind the Imam.