Also, if you have added a service using the MapServices widget, it will "confuse" things as well.
Well, just tested this a little more.
have a fv34 app with nav, overview, coordinate, headercontroller and layerlist widgets, and no others.
I still get this weird behaviour. If I click, move down, it works fine, if I tell the same layer to move down again, or for that matter, tell it to move up, it will jump down 5 positions. Doesn't matter which way I tell it to move, after the second click, it will jump down like 5 positions. Once it moves all the way to the bottom, the move up will work again twice, then will ignore all the move ups you send it until you move down again..
R_
seems to do it in fv33 as well. However, my FV31 project works fine until I add a layer using MapServices widget, and load at bottom, then it behaves the similar