For quite a while (maybe forever), there's been a bug when dimensioning a drawing view.  If you'd right-click on an edge and choose "Select Midpoint" from the drop-down, and then move your cursor to your second selection it wouldn't turn orange to show what you were about to select (this is assuming you have "Dynamic Highlight" turned on).  I had gotten into the habit of choosing the other edge first, but of course when dimensioning between two midpoints (which I frequently need to do) this didn't work.  I haven't seen anything reported about it, but I just noticed that it has apparently been fixed with SW2016.