That happens to me a lot when i am at all day sewing meetings or a weekend retreat! For me it seems to “happen” on the easiest blocks! One time my quilting buddy and i were at a 3 day retreat and both making quilts with the Split Decision pattern, which is kinda like a rail fence with an extra step. You wouldnt believe how many times we both had to tear out what we had sewn - happened so many times that we laughed so hard we were in tears and provided a lot of comic relief for the rest of the group!