I'm not sure how to explain this. You know how you can click anywhere on the map, and if the pusher has a clear path there, it will run to that spot? If I start pressing the arrow keys before the animation is finished, sometimes, instead of pushing the box, the pusher will end up superimposed over the box and the box disappears. The box will reappear when pushed, only to disappear a little later (I'm never sure when), but it reappears again if pushed (and then doesn't disappear again).
Did that make sense?
And also, it doesn't seem to matter what skin I'm using, although I admit I only ever use two skins -- Classic and Warehouse Man. It's happened with both.