We (mainly @chi_t_williams) looked at the 78 worst Waymo crashes of the last seven months. The vast majority (60 out of 78) were "human rear-ends Waymo" and/or "human hits stationary Waymo."
And no, this isn't because erratic Waymo behavior leads to more rear-end crashes. Waymo's overall crash rate is much lower than those of human drivers in the cities where Waymo operates. So humans hit Waymos less often than they hit other humans and Waymos hit humans *way* less.