I am working it a drawing that is very large, and I am sure that I have Automatic Solve checked on. If I move a line within my sketch, and then try to undo it, using either the button under tools or the CRTL+Z command, and it will not return to its original position. However, I can put a dimension on that same line and change the dimension, and when I try to undo this, it will work fine, undoing the dimension change, and then the dimension itself. Attached is my file.