When zoomed in on the block diagram, and debugging, every time you step forward or hit a breakpoint, LabVIEW tries to jump the display to show the current execution location, but it does so based on the un-zoomed location. The result is that if you are zoomed in, the spot LV visually jumps to is somewhere out in empty space. Generally, if you are zoomed in, the spot it jumps to is in the empty space to the upper-left of your diagram, presumably because that would be the correct location if you were not zoomed in.
If you zoom back out to actual size, everything works properly. However, this is surely not the intended behavior.