Mantras are only endowed with transformative energy if offered in initiation (dīkṣa) in the mouth of the guru. It isn't so much accurate pronunciation, but fairly the power with which the mantra is endowed that offers it transforming capability. Cundī dhāraṇī or mantra also 1st appeared within the Kāraṇḍavyūhasūtra: namaḥ https://www.youtube.com/@Mahavidyabaglamukhi/