Imam Al-Haramayn Al-Juwayni recorded the opinion that Uzayr was the one who corrupted the Torah. I believe it was his own opinion, but can't remember for sure. According to Jewish tradition, Uzayr (or Esra) was the one who started the canonization of the Tanakh. So when did any corruption take place? Most likely not after the time of Uzayr, since you will find manuscripts, scholarly quotes from after that etc.