I cannot get this cheevo either. I sat in two hours of Zoom meetings while mindlessly clicking PLAY! over and over and over... and. over. I went down below 1000 eternals and back up over 1600 twice. I had at least a dozen 777s. Still no cheevo :,(
PS - yes I'm playing Eterum while on Zoom meetings. Just to get the achievements, I swear! ;)
PPS - I love this mod. Thank you. I literally LOL'd when I got "Fatal Mistake" without realizing it.