My model in a part file without any external references has taken up moving as a whole vertically, away from the base sketch on the front plane. If I move the history bar one feature up (or more) it returns to the expected position. It doesn't matter what the last feature is, the behaviour is the same. If I delete the last feature the error just moves to the previous feature, and still corrects when I move the bar up one or more steps. Anytime the entire list is active the error is there.
I've checked that my base sketch is locked to the top plane (visible in images below,) as is the trimming sketch on the right plane. The movement is 13.51mm in Y which does not appear to correspond to any dims I have.
I've seen this before and have always ended up redrawing the entire model to correct it. Any ideas?