Does it invalidate the prayer if someone who is not part of the congregation corrects the imam's mistake?

If the imam makes a mistake during recitation or cannot remember the next part to recite, and someone from the congregation corrects or reminds him, neither the congregation's nor the imam's prayer is invalidated. (Merğînânî, el-Hidâye, 1/62-63; Mevsılî, el-İhtiyâr, 1/60-61) However, if someone who is not part of the congregation corrects the imam's mistake and the imam acts upon this correction, the prayer becomes invalid. This is because such an action is considered as teaching and learning. (Zeylaî, Tebyîn, 1/156; el-Fetâva’l-Hindiyye, 1/99) In some other schools of thought, however, this correction is not regarded as something that invalidates the prayer. According to a narration, while Hz. Osman (r.a.) was sitting at Maqam Ibrahim, he corrected the mistake of someone praying nearby in this manner. (İbn Kudâme, el-Muğnî, 2/45)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu